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<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8">
<title>The Complete JavaScript Reference Guide</title>
<link rel="stylesheet" href="./style.css">
</head>
<body>
<article class="h-entry">
<header>
<h1 class="p-name">The Complete JavaScript Reference Guide</h1>
</header>
<section data-field="subtitle" class="p-summary">
You will want to bookmark this
</section>
<section data-field="body" class="e-content">
<section name="6a85" class="section section--body section--first">
<div class="section-divider">
<hr class="section-divider">
</div>
<div class="section-content">
<div class="section-inner sectionLayout--insetColumn">
<h3 name="8be9" id="8be9" class="graf graf--h3 graf--leading graf--title">The Complete JavaScript
Reference Guide</h3>
<figure name="85b6" id="85b6" class="graf graf--figure graf-after--h3"><img class="graf-image"
data-image-id="0*In5wB-29T0Ud_zs3.jpg" data-width="600" data-height="431"
src="https://cdn-images-1.medium.com/max/800/0*In5wB-29T0Ud_zs3.jpg"></figure>
<h3 name="6610" id="6610" class="graf graf--h3 graf-after--figure">How to learn effectively</h3>
<p name="22c5" id="22c5" class="graf graf--p graf-after--h3"><strong
class="markup--strong markup--p-strong">Learning</strong>: The acquisition of skills and the ability
to apply them in the future.</p>
<p name="2b6e" id="2b6e" class="graf graf--p graf-after--p"><strong
class="markup--strong markup--p-strong">What makes an Effective learner?</strong></p>
<ul class="postList">
<li name="7504" id="7504" class="graf graf--li graf-after--p">They are active listeners.</li>
<li name="179b" id="179b" class="graf graf--li graf-after--li">They are engaged with the material.</li>
<li name="3193" id="3193" class="graf graf--li graf-after--li">They are receptive of feedback.</li>
<li name="17d8" id="17d8" class="graf graf--li graf-after--li">They are open to difficulty.</li>
</ul>
<p name="d1f4" id="d1f4" class="graf graf--p graf-after--li"><strong
class="markup--strong markup--p-strong">Why do active learning techniques feel difficult?</strong></p>
<ul class="postList">
<li name="7848" id="7848" class="graf graf--li graf-after--p">It feels difficult because you are
constantly receiving feedback, and so you are constantly adapting and perfecting the material.</li>
</ul>
<p name="2f3a" id="2f3a" class="graf graf--p graf-after--li"><strong
class="markup--strong markup--p-strong">Desirable Difficulty</strong></p>
<ul class="postList">
<li name="67c9" id="67c9" class="graf graf--li graf-after--p">The skills we wish to obtain is often a
difficult one.</li>
<li name="c939" id="c939" class="graf graf--li graf-after--li">We want challenging but possible lessons
based on current level of skill.</li>
</ul>
<p name="d5ff" id="d5ff" class="graf graf--p graf-after--li"><strong
class="markup--strong markup--p-strong">Effective learners space their practice</strong></p>
<ul class="postList">
<li name="59a4" id="59a4" class="graf graf--li graf-after--p graf--trailing">Consistent effort >
cramming => for <strong class="markup--strong markup--li-strong">durable knowledge</strong></li>
</ul>
</div>
</div>
</section>
<section name="bd60" class="section section--body section--last">
<div class="section-divider">
<hr class="section-divider">
</div>
<div class="section-content">
<div class="section-inner sectionLayout--insetColumn">
<h3 name="98cc" id="98cc" class="graf graf--h3 graf--leading">Getting visual feedback in your programs
</h3>
<p name="f1ec" id="f1ec" class="graf graf--p graf-after--h3">The first command we’ll learn in JavaScript
is <code class="markup--code markup--p-code">console.log</code>. This command is used to <em
class="markup--em markup--p-em">print</em> something onto the screen. As we write our first lines of
code, we’ll be using <code class="markup--code markup--p-code">console.log</code> frequently as a way to
visually see the output of our programs. Let’s write our first program:</p>
<pre name="e289" id="e289"
class="graf graf--pre graf-after--p"><code class="markup--code markup--pre-code">console.log("hello world");<br>console.log("how are you?");</code></pre>
<p name="dd88" id="dd88" class="graf graf--p graf-after--pre">Executing the program above would print out
the following:</p>
<pre name="ac39" id="ac39"
class="graf graf--pre graf-after--p"><code class="markup--code markup--pre-code">hello world<br>how are you?</code></pre>
<p name="be82" id="be82" class="graf graf--p graf-after--pre">Nothing too ground breaking here, but pay
close attention to the exact way we wrote the program. In particular, notice how we lay out the periods,
parentheses, and quotation marks. We’ll also terminate lines with semicolons (;).</p>
<blockquote name="8b89" id="8b89" class="graf graf--blockquote graf-after--p"><em
class="markup--em markup--blockquote-em">Depending on how you structure your code, sometimes you’ll be
able to omit semicolons at the end of lines. For now, you’ll want to include them just as we do.</em>
</blockquote>
<h3 name="2a8a" id="2a8a" class="graf graf--h3 graf-after--blockquote">Syntax</h3>
<p name="e7e2" id="e7e2" class="graf graf--p graf-after--h3">We refer to the exact arrangement of the
symbols, characters, and keywords as <strong class="markup--strong markup--p-strong">syntax</strong>.
These details matter — your computer will only be able to “understand” proper JavaScript syntax. A
programming language is similar to a spoken language. A spoken language like English has grammar rules
that we should follow in order to be understood by fellow speakers. In the same way, a programming
language like JavaScript has syntax rules that we ought to follow!</p>
<p name="14b7" id="14b7" class="graf graf--p graf-after--p">As you write your first lines of code in this
new language, you may make many syntax errors. Don’t get frustrated! This is normal — all new
programmers go through this phase. Every time we recognize an error in our code, we have an opportunity
to reinforce your understanding of correct syntax. Adopt a growth mindset and learn from your mistakes.
</p>
<p name="3277" id="3277" class="graf graf--p graf-after--p">Additionally, one of the best things about
programming is that we can get such immediate feedback from our creations. There is no penalty for
making a mistake when programming. Write some code, run the code, read the errors, fix the errors, rinse
and repeat!</p>
<h3 name="3ed2" id="3ed2" class="graf graf--h3 graf-after--p">Code comments</h3>
<p name="d005" id="d005" class="graf graf--p graf-after--h3">Occasionally we’ll want to leave <strong
class="markup--strong markup--p-strong">comments</strong> or notes in our code. Commented lines will
be ignored by our computer. This means that we can use comments to write plain english or temporarily
avoid execution of some JavaScript lines. The proper <em class="markup--em markup--p-em">syntax</em> for
writing a comment is to begin the line with double forward slashes (<code
class="markup--code markup--p-code">//</code>):</p>
<pre name="f4e6" id="f4e6"
class="graf graf--pre graf-after--p"><code class="markup--code markup--pre-code">// let's write another program!!!<br>console.log("hello world");</code></pre>
<pre name="e986" id="e986"
class="graf graf--pre graf-after--pre"><code class="markup--code markup--pre-code">// console.log("how are you?");</code></pre>
<pre name="3bc4" id="3bc4"
class="graf graf--pre graf-after--pre"><code class="markup--code markup--pre-code">console.log("goodbye moon");</code></pre>
<p name="dadb" id="dadb" class="graf graf--p graf-after--pre">The program above would only print:</p>
<pre name="bf40" id="bf40"
class="graf graf--pre graf-after--p"><code class="markup--code markup--pre-code">hello world<br>goodbye moon</code></pre>
<p name="c221" id="c221" class="graf graf--p graf-after--pre">Comments are useful when annotating pieces
of code to offer an explanation of how the code works. We’ll want to strive to write straightforward
code that is self-explanatory when possible, but we can also use comments to add additional clarity. The
real art of programming is to write code so elegantly that it is easy to follow.</p>
<p name="e47b" id="e47b" class="graf graf--p graf-after--p"><strong
class="markup--strong markup--p-strong">The Number Data Type</strong></p>
<p name="4c3e" id="4c3e" class="graf graf--p graf-after--p">The <strong
class="markup--strong markup--p-strong">number</strong> data type in JS is used to represent any
numerical values, including integers and decimal numbers.</p>
<p name="10b1" id="10b1" class="graf graf--p graf-after--p"><strong
class="markup--strong markup--p-strong">Basic Arithmetic Operators</strong></p>
<p name="c235" id="c235" class="graf graf--p graf-after--p">Operators are the symbols that perform
particular operations.</p>
<ul class="postList">
<li name="f533" id="f533" class="graf graf--li graf-after--p"><strong
class="markup--strong markup--li-strong">+</strong> (addition)</li>
<li name="5b9f" id="5b9f" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">-</strong> (subtraction)</li>
<li name="b98b" id="b98b" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">asterisk</strong> (multiplication)</li>
<li name="9a15" id="9a15" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">/</strong> (division)</li>
<li name="c752" id="c752" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">%</strong> (modulo)</li>
</ul>
<p name="181c" id="181c" class="graf graf--p graf-after--li">JS evaluates more complex expressions using
the general math order of operations aka PEMDAS.</p>
<ul class="postList">
<li name="b6e3" id="b6e3" class="graf graf--li graf-after--p"><strong
class="markup--strong markup--li-strong">PEMDAS</strong> : Parentheses, Exponents, Multiplication,
Division, Modulo, Addition, Subtraction.</li>
<li name="9c25" id="9c25" class="graf graf--li graf-after--li"><em class="markup--em markup--li-em">To
force a specific order of operation, use the group operator ( ) around a part of the
expression.</em></li>
</ul>
<p name="ac24" id="ac24" class="graf graf--p graf-after--li"><strong
class="markup--strong markup--p-strong">Modulo</strong> : Very useful operation to check divisibility
of numbers, check for even & odd, whether a number is prime, and much more! <em
class="markup--em markup--p-em">(Discrete Math concept, circular problems can be solved with
modulo)</em></p>
<ul class="postList">
<li name="cf5b" id="cf5b" class="graf graf--li graf-after--p">Whenever you have a smaller number % a
larger number, the answer will just be the initial small number. <br> console.log(7 % 10) // => 7;
</li>
</ul>
<p name="1742" id="1742" class="graf graf--p graf-after--li"><strong
class="markup--strong markup--p-strong">The String Data Type</strong></p>
<p name="9a89" id="9a89" class="graf graf--p graf-after--p">The <strong
class="markup--strong markup--p-strong">string</strong> data type is a primitive data type that used
to represent textual data.</p>
<ul class="postList">
<li name="e1b0" id="e1b0" class="graf graf--li graf-after--p">can be wrapped by either <strong
class="markup--strong markup--li-strong">single</strong> or <strong
class="markup--strong markup--li-strong">double</strong> quotation marks, <em
class="markup--em markup--li-em">best to choose one and stick with it for consistency</em>.</li>
<li name="f8ad" id="f8ad" class="graf graf--li graf-after--li">If your string contains quotation marks
inside, can layer single or double quotation marks to allow it to work.<br> “That’s a great string”;
(valid)<br> <br> ‘Shakespeare wrote, “To be or not to be”’; (valid)<br> <br> ‘That’s a bad string’;
(invalid)</li>
<li name="b2cb" id="b2cb" class="graf graf--li graf-after--li">Alt. way to add other quotes within
strings is to use template literals.<br> `This is a temp’l’ate literal ${function}` // use ${} to
invoke functions within.</li>
<li name="7b1a" id="7b1a" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">.length</strong> : property that can be appended to data to
return the length.</li>
<li name="f633" id="f633" class="graf graf--li graf-after--li">empty strings have a length of zero.</li>
<li name="0a07" id="0a07" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">indices</strong> : indexes of data that begin at 0, can
call upon index by using the bracket notation [ ].<br> console.log(“bootcamp”[0]); // =>
“b”<br> console.log(“bootcamp”[10]); // => “undefined”<br> console.log(“boots”[1 * 2]); // =>
“o”<br> console.log(“boots”[“boot”.length-1]); // => “t”</li>
<li name="6482" id="6482" class="graf graf--li graf-after--li">we can pass expressions through the
brackets as well since JS always evaluates expressions first.</li>
<li name="e2f5" id="e2f5" class="graf graf--li graf-after--li">The index of the last character of a
string is always one less than it’s length.</li>
<li name="2271" id="2271" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">indexOf()</strong> : method used to find the first index of
a given character within a string.<br> console.log(“bagel”.indexOf(“b”)); // =>
0<br> console.log(“bagel”.indexOf(“z”)); // => -1</li>
<li name="8d68" id="8d68" class="graf graf--li graf-after--li">if the character inside the indexOf()
search does not exist in the string, the output will be -1.</li>
<li name="d15e" id="d15e" class="graf graf--li graf-after--li">the indexOf() search will return the
first instanced index of the the char in the string.</li>
<li name="a275" id="a275" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">concatenate</strong> : word to describe joining strings
together into a single string.</li>
</ul>
<p name="fa5e" id="fa5e" class="graf graf--p graf-after--li"><strong
class="markup--strong markup--p-strong">The Boolean Data Type</strong></p>
<p name="a909" id="a909" class="graf graf--p graf-after--p">The <strong
class="markup--strong markup--p-strong">Boolean</strong> data type is the simplest data type since
there are only two values: <strong class="markup--strong markup--p-strong">true</strong> and <strong
class="markup--strong markup--p-strong">false</strong>.</p>
<ul class="postList">
<li name="60da" id="60da" class="graf graf--li graf-after--p"><strong
class="markup--strong markup--li-strong">Logical Operators</strong> (B<em
class="markup--em markup--li-em">oolean Operators</em>) are used to establish logic in our code.
</li>
<li name="139b" id="139b" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">!</strong> (not) : reverses a Boolean
value.<br> console.log(!true); // => false<br> console.log(!!false); // => false</li>
<li name="e412" id="e412" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">Logical Order of Operations</strong> : JS will evaluate !,
then &&, then ||.</li>
<li name="99ad" id="99ad" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">Short-Circuit Evaluation</strong> : Because JS evalutes
from left to right, expressions can “short-circuit”. For example if we have true on the left of an ||
logical comparison, it will stop evaluating and yield true instead of wasting resources on processing
the rest of the statement.<br> console.log(true || !false) // => stops after it sees “true ||”</li>
</ul>
<p name="d6c3" id="d6c3" class="graf graf--p graf-after--li"><strong
class="markup--strong markup--p-strong">Comparison Operators</strong></p>
<p name="76c7" id="76c7" class="graf graf--p graf-after--p">All comparison operators will result in a
boolean output.</p>
<p name="3a93" id="3a93" class="graf graf--p graf-after--p"><strong
class="markup--strong markup--p-strong">The relative comparators</strong></p>
<ul class="postList">
<li name="6fee" id="6fee" class="graf graf--li graf-after--p"><strong
class="markup--strong markup--li-strong">></strong> (greater than)</li>
<li name="0437" id="0437" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong"><</strong> (less than)</li>
<li name="17ff" id="17ff" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">>=</strong> (greater than or equal to)</li>
<li name="b2b4" id="b2b4" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong"><=</strong> (less than or equal to)</li>
<li name="0c13" id="0c13" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">===</strong> (equal to)</li>
<li name="b73a" id="b73a" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">!==</strong> (not equal to)</li>
</ul>
<p name="50be" id="50be" class="graf graf--p graf-after--li">Fun Fact: “a” < “b” is considered valid JS
Code because string comparisons are compared lexicographically (meaning dictionary order), so “a” is
less than “b” because it appears earlier!</p>
<p name="a833" id="a833" class="graf graf--p graf-after--p">If there is ever a standstill comparison of
two string lexicographically (i.e. app vs apple) the comparison will deem the shorter string lesser.</p>
<p name="9398" id="9398" class="graf graf--p graf-after--p"><strong
class="markup--strong markup--p-strong">Difference between == and ===</strong></p>
<h4 name="b620" id="b620" class="graf graf--h4 graf-after--p">===</h4>
<p name="6010" id="6010" class="graf graf--p graf-after--h4">Strict Equality, will only return true if the
two comparisons are entirely the same.</p>
<h4 name="38a2" id="38a2" class="graf graf--h4 graf-after--p">==</h4>
<p name="2ae2" id="2ae2" class="graf graf--p graf-after--h4">Loose Equality, will return true even if the
values are of a different type, due to coercion. (Avoid using this)</p>
<p name="18bf" id="18bf" class="graf graf--p graf-after--p"><strong
class="markup--strong markup--p-strong">Variables</strong></p>
<p name="20d1" id="20d1" class="graf graf--p graf-after--p">Variables are used to store information to be
referenced and manipulated in a program.</p>
<ul class="postList">
<li name="c73d" id="c73d" class="graf graf--li graf-after--p">We initialize a variable by using the
<strong class="markup--strong markup--li-strong">let</strong> keyword and a <strong
class="markup--strong markup--li-strong">=</strong> single equals sign (assignment
operator). <br> let bootcamp = “App Academy”;<br> console.log(bootcamp); // “App Academy”</li>
<li name="7849" id="7849" class="graf graf--li graf-after--li">JS variable names can contain any
alphanumeric characters, underscores, or dollar signs (cannot being with a number).</li>
<li name="ad76" id="ad76" class="graf graf--li graf-after--li">If you do not declare a value for a
variable, undefined is automatically set. <br> let bootcamp;<br> console.log(bootcamp); // undefined
</li>
<li name="2188" id="2188" class="graf graf--li graf-after--li">We can change the value of a previously
declared variable (let, not const) by re-assigning it another value.</li>
<li name="47ca" id="47ca" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">let</strong> is the updated version of <strong
class="markup--strong markup--li-strong">var</strong>; there are some differences in terms of
hoisting and global/block scope</li>
</ul>
<p name="63b9" id="63b9" class="graf graf--p graf-after--li"><strong
class="markup--strong markup--p-strong">Assignment Shorthand</strong></p>
<p name="8d9f" id="8d9f" class="graf graf--p graf-after--p">let num = 0;<br> num += 10; // same as num =
num + 10<br> num -= 2; // same as num = num — 2<br> num /= 4; // same as num = num / 4<br> num *= 7; //
same as num = num * 7</p>
<ul class="postList">
<li name="9c05" id="9c05" class="graf graf--li graf-after--p">In general, any nonsensical arithmetic
will result in <strong class="markup--strong markup--li-strong">NaN</strong> ; usually operations that
include undefined.</li>
</ul>
<p name="50e6" id="50e6" class="graf graf--p graf-after--li"><strong
class="markup--strong markup--p-strong">Functions</strong></p>
<p name="468d" id="468d" class="graf graf--p graf-after--p">A function is a procedure of code that will
run when called. Functions are used so that we do not have to rewrite code to do the same thing over and
over. (Think of them as ‘subprograms’)</p>
<ul class="postList">
<li name="366f" id="366f" class="graf graf--li graf-after--p"><strong
class="markup--strong markup--li-strong">Function Declaration</strong> : Process when we first
initially write our function.</li>
<li name="676f" id="676f" class="graf graf--li graf-after--li">Includes three things:</li>
<li name="80c2" id="80c2" class="graf graf--li graf-after--li">Name of the function.</li>
<li name="f3a4" id="f3a4" class="graf graf--li graf-after--li">A list of <em
class="markup--em markup--li-em">parameters</em> ()</li>
<li name="2b0e" id="2b0e" class="graf graf--li graf-after--li">The code to execute {}</li>
<li name="6879" id="6879" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">Function Calls</strong> : We can call upon our function
whenever and wherever* we want. (*wherever is only after the initial declaration)</li>
<li name="8374" id="8374" class="graf graf--li graf-after--li">JS evaluates code top down, left to
right.</li>
<li name="2687" id="2687" class="graf graf--li graf-after--li">When we execute a declared function later
on in our program we refer to this as <strong
class="markup--strong markup--li-strong">invoking</strong> our function.</li>
<li name="0c3a" id="0c3a" class="graf graf--li graf-after--li">Every function in JS returns undefined
unless otherwise specified.</li>
<li name="4207" id="4207" class="graf graf--li graf-after--li">When we hit a <strong
class="markup--strong markup--li-strong">return</strong> statement in a function we immediately exit
the function and return to where we called the function.</li>
<li name="e39f" id="e39f" class="graf graf--li graf-after--li">When naming functions in JS always use
camelCase and name it something appropriate.</li>
</ul>
<p name="e4ad" id="e4ad" class="graf graf--p graf-after--li">Greate code reads like English and almost
explains itself. Think: Elegant, readable, and maintainable!</p>
<p name="1728" id="1728" class="graf graf--p graf-after--p"><strong
class="markup--strong markup--p-strong">Parameters and Arguments</strong></p>
<ul class="postList">
<li name="e94e" id="e94e" class="graf graf--li graf-after--p"><strong
class="markup--strong markup--li-strong">Parameters</strong> : Comma seperated variables specified
as part of a function’s declaration.</li>
<li name="6740" id="6740" class="graf graf--li graf-after--li"><strong
class="markup--strong markup--li-strong">Arguments</strong> : Values passed to the function when it
is invoked.</li>
<li name="004c" id="004c" class="graf graf--li graf-after--li"><em class="markup--em markup--li-em">If
the number of arguments passed during a function invocation is different than the number of
paramters listed, it will still work.</em></li>
<li name="7da5" id="7da5" class="graf graf--li graf-after--li">However, is there are not enough
arguments provided for parameters our function will likely yield <strong
class="markup--strong markup--li-strong">Nan</strong>.</li>
</ul>
<h3 name="766c" id="766c" class="graf graf--h3 graf-after--li">Including Comments</h3>
<p name="44bb" id="44bb" class="graf graf--p graf-after--h3">Comments are important because they help
other people understand what is going on in your code or remind you if you forgot something yourself.
Keep in mind that they have to be marked properly so the browser won’t try to execute them.</p>
<p name="fc90" id="fc90" class="graf graf--p graf-after--p">In JavaScript you have two different options:
</p>
<ul class="postList">
<li name="356d" id="356d" class="graf graf--li graf-after--p">Single-line comments — To include a
comment that is limited to a single line, precede it with <code
class="markup--code markup--li-code">//</code></li>
<li name="ee3a" id="ee3a" class="graf graf--li graf-after--li">Multi-line comments — In case you want to
write longer comments between several lines, wrap it in <code
class="markup--code markup--li-code">/*</code> and <code
class="markup--code markup--li-code">*/</code> to avoid it from being executed</li>
</ul>
<h3 name="0fae" id="0fae" class="graf graf--h3 graf-after--li">Variables in JavaScript</h3>
<p name="a118" id="a118" class="graf graf--p graf-after--h3">Variables are stand-in values that you can
use to perform operations. You should be familiar with them from math class.</p>
<h3 name="c890" id="c890" class="graf graf--h3 graf-after--p">var, const, let</h3>
<p name="52c1" id="52c1" class="graf graf--p graf-after--h3">You have three different possibilities for
declaring a variable in JavaScript, each with their own specialties:</p>
<ul class="postList">
<li name="4b29" id="4b29" class="graf graf--li graf-after--p"><code
class="markup--code markup--li-code">var</code> — The most common variable. It can be reassigned but
only accessed within a function. Variables defined with <code
class="markup--code markup--li-code">var</code> move to the top when the code is executed.</li>
<li name="d234" id="d234" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">const</code> — Can not be reassigned and not accessible before
they appear within the code.</li>
<li name="0e3b" id="0e3b" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">let</code> — Similar to <code
class="markup--code markup--li-code">const</code>, the <code
class="markup--code markup--li-code">let</code> variable can be reassigned but not re-declared.</li>
</ul>
<h3 name="523d" id="523d" class="graf graf--h3 graf-after--li">Data Types</h3>
<p name="b6f8" id="b6f8" class="graf graf--p graf-after--h3">Variables can contain different types of
values and data types. You use <code class="markup--code markup--p-code">=</code> to assign them:</p>
<ul class="postList">
<li name="b276" id="b276" class="graf graf--li graf-after--p">Numbers — <code
class="markup--code markup--li-code">var age = 23</code></li>
<li name="5571" id="5571" class="graf graf--li graf-after--li">Variables — <code
class="markup--code markup--li-code">var x</code></li>
<li name="e26c" id="e26c" class="graf graf--li graf-after--li">Text (strings) — <code
class="markup--code markup--li-code">var a = "init"</code></li>
<li name="1312" id="1312" class="graf graf--li graf-after--li">Operations — <code
class="markup--code markup--li-code">var b = 1 + 2 + 3</code></li>
<li name="9880" id="9880" class="graf graf--li graf-after--li">True or false statements — <code
class="markup--code markup--li-code">var c = true</code></li>
<li name="335a" id="335a" class="graf graf--li graf-after--li">Constant numbers — <code
class="markup--code markup--li-code">const PI = 3.14</code></li>
<li name="7221" id="7221" class="graf graf--li graf-after--li">Objects — <code
class="markup--code markup--li-code">var name = {firstName:"John",
lastName:"Doe"}</code></li>
</ul>
<p name="3353" id="3353" class="graf graf--p graf-after--li">There are more possibilities. Note that
variables are case sensitive. That means <code class="markup--code markup--p-code">lastname</code> and
<code class="markup--code markup--p-code">lastName</code> will be handled as two different variables.
</p>
<h3 name="9088" id="9088" class="graf graf--h3 graf-after--p">Objects</h3>
<p name="a5c8" id="a5c8" class="graf graf--p graf-after--h3">Objects are certain kinds of variables. They
are variables that can have their own values and methods. The latter are actions that you can perform on
objects.</p>
<p name="99ba" id="99ba" class="graf graf--p graf-after--p">var person = {</p>
<p name="c312" id="c312" class="graf graf--p graf-after--p">firstName:”John”,</p>
<p name="f94c" id="f94c" class="graf graf--p graf-after--p">lastName:”Doe”,</p>
<p name="1c03" id="1c03" class="graf graf--p graf-after--p">age:20,</p>
<p name="3956" id="3956" class="graf graf--p graf-after--p">nationality:”German”</p>
<p name="10ac" id="10ac" class="graf graf--p graf-after--p">};</p>
<h3 name="d6ff" id="d6ff" class="graf graf--h3 graf-after--p">The Next Level: Arrays</h3>
<p name="484a" id="484a" class="graf graf--p graf-after--h3">Next up in our JavaScript cheat sheet are
arrays. Arrays are part of many different programming languages. They are a way of organizing variables
and properties into groups. Here’s how to create one in JavaScript:</p>
<p name="962c" id="962c" class="graf graf--p graf-after--p">var fruit = [“Banana”, “Apple”, “Pear”];</p>
<p name="46fd" id="46fd" class="graf graf--p graf-after--p">Now you have an array called <code
class="markup--code markup--p-code">fruit</code> which contains three items that you can use for
future operations.</p>
<h3 name="106f" id="106f" class="graf graf--h3 graf-after--p">Array Methods</h3>
<p name="fc74" id="fc74" class="graf graf--p graf-after--h3">Once you have created arrays, there are a few
things you can do with them:</p>
<ul class="postList">
<li name="4e4b" id="4e4b" class="graf graf--li graf-after--p"><code
class="markup--code markup--li-code">concat()</code> — Join several arrays into one</li>
<li name="5c02" id="5c02" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">indexOf()</code> — Returns the first position at which a given
element appears in an array</li>
<li name="45cd" id="45cd" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">join()</code> — Combine elements of an array into a single
string and return the string</li>
<li name="3a4e" id="3a4e" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">lastIndexOf()</code> — Gives the last position at which a given
element appears in an array</li>
<li name="8fbb" id="8fbb" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">pop()</code> — Removes the last element of an array</li>
<li name="28e4" id="28e4" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">push()</code> — Add a new element at the end</li>
<li name="0be2" id="0be2" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">reverse()</code> — Sort elements in a descending order</li>
<li name="775e" id="775e" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">shift()</code> — Remove the first element of an array</li>
<li name="1063" id="1063" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">slice()</code> — Pulls a copy of a portion of an array into a
new array</li>
<li name="53fd" id="53fd" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">sort()</code> — Sorts elements alphabetically</li>
<li name="f551" id="f551" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">splice()</code> — Adds elements in a specified way and position
</li>
<li name="c46b" id="c46b" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">toString()</code> — Converts elements to strings</li>
<li name="ef66" id="ef66" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">unshift()</code> —Adds a new element to the beginning</li>
<li name="4598" id="4598" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">valueOf()</code> — Returns the primitive value of the specified
object</li>
</ul>
<h3 name="3d59" id="3d59" class="graf graf--h3 graf-after--li">Operators</h3>
<p name="4469" id="4469" class="graf graf--p graf-after--h3">If you have variables, you can use them to
perform different kinds of operations. To do so, you need operators.</p>
<h3 name="bc32" id="bc32" class="graf graf--h3 graf-after--p">Basic Operators</h3>
<ul class="postList">
<li name="5d34" id="5d34" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">+</code> — Addition</li>
<li name="5fd9" id="5fd9" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">-</code> — Subtraction</li>
<li name="3b13" id="3b13" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">*</code> — Multiplication</li>
<li name="521a" id="521a" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">/</code> — Division</li>
<li name="cf0f" id="cf0f" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">(...)</code> — Grouping operator, operations within brackets
are executed earlier than those outside</li>
<li name="bb2a" id="bb2a" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">%</code> — Modulus (remainder )</li>
<li name="e837" id="e837" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">++</code> — Increment numbers</li>
<li name="71ea" id="71ea" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">--</code> — Decrement numbers</li>
</ul>
<h3 name="5c56" id="5c56" class="graf graf--h3 graf-after--li">Comparison Operators</h3>
<ul class="postList">
<li name="a2b0" id="a2b0" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">==</code> — Equal to</li>
<li name="5105" id="5105" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">===</code> — Equal value and equal type</li>
<li name="c79c" id="c79c" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">!=</code> — Not equal</li>
<li name="1f7f" id="1f7f" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">!==</code> — Not equal value or not equal type</li>
<li name="78c3" id="78c3" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">></code> — Greater than</li>
<li name="d40b" id="d40b" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code"><</code> — Less than</li>
<li name="081b" id="081b" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">>=</code> — Greater than or equal to</li>
<li name="d065" id="d065" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code"><=</code> — Less than or equal to</li>
<li name="174d" id="174d" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">?</code> — Ternary operator</li>
</ul>
<h3 name="3394" id="3394" class="graf graf--h3 graf-after--li">Logical Operators</h3>
<ul class="postList">
<li name="cb7b" id="cb7b" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">&&</code> — Logical and</li>
<li name="b1ee" id="b1ee" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">||</code> — Logical or</li>
<li name="96d4" id="96d4" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">!</code> — Logical not</li>
</ul>
<h3 name="8145" id="8145" class="graf graf--h3 graf-after--li">Bitwise Operators</h3>
<ul class="postList">
<li name="8cf7" id="8cf7" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">&</code> — AND statement</li>
<li name="02d5" id="02d5" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">|</code> — OR statement</li>
<li name="e576" id="e576" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">~</code> — NOT</li>
<li name="9c66" id="9c66" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">^</code> — XOR</li>
<li name="b343" id="b343" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code"><<</code> — Left shift</li>
<li name="52b1" id="52b1" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">>></code> — Right shift</li>
<li name="1b5c" id="1b5c" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">>>></code> — Zero fill right shift</li>
</ul>
<h3 name="3ed3" id="3ed3" class="graf graf--h3 graf-after--li">Functions</h3>
<p name="329c" id="329c" class="graf graf--p graf-after--h3">JavaScript functions are blocks of code that
perform a certain task. A basic function looks like this:</p>
<p name="7f2c" id="7f2c" class="graf graf--p graf-after--p">function name(parameter1, parameter2,
parameter3) {</p>
<p name="909f" id="909f" class="graf graf--p graf-after--p">// what the function does</p>
<p name="e5e5" id="e5e5" class="graf graf--p graf-after--p">}</p>
<p name="0cf2" id="0cf2" class="graf graf--p graf-after--p">As you can see, it consists of the <code
class="markup--code markup--p-code">function</code> keyword plus a name. The function’s parameters are
in the brackets and you have curly brackets around what the function performs. You can create your own,
but to make your life easier – there are also a number of default functions.</p>
<h3 name="c58d" id="c58d" class="graf graf--h3 graf-after--p">Outputting Data</h3>
<p name="6f3c" id="6f3c" class="graf graf--p graf-after--h3">A common application for functions is the
output of data. For the output, you have the following options:</p>
<ul class="postList">
<li name="a7a7" id="a7a7" class="graf graf--li graf-after--p"><code
class="markup--code markup--li-code">alert()</code> — Output data in an alert box in the browser
window</li>
<li name="0c44" id="0c44" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">confirm()</code> — Opens up a yes/no dialog and returns
true/false depending on user click</li>
<li name="9690" id="9690" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">console.log()</code> — Writes information to the browser
console, good for debugging purposes</li>
<li name="0d4d" id="0d4d" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">document.write()</code> — Write directly to the HTML document
</li>
<li name="16aa" id="16aa" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">prompt()</code> — Creates a dialogue for user input</li>
</ul>
<h3 name="6b28" id="6b28" class="graf graf--h3 graf-after--li">Global Functions</h3>
<p name="a069" id="a069" class="graf graf--p graf-after--h3">Global functions are functions built into
every browser capable of running JavaScript.</p>
<ul class="postList">
<li name="f4f1" id="f4f1" class="graf graf--li graf-after--p"><code
class="markup--code markup--li-code">decodeURI()</code> — Decodes a <a
href="https://en.wikipedia.org/wiki/Uniform_Resource_Identifier"
data-href="https://en.wikipedia.org/wiki/Uniform_Resource_Identifier"
class="markup--anchor markup--li-anchor" rel="noopener noreferrer noopener" target="_blank">Uniform
Resource Identifier (URI)</a> created by <code class="markup--code markup--li-code">encodeURI</code>
or similar</li>
<li name="c203" id="c203" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">decodeURIComponent()</code> — Decodes a URI component</li>
<li name="176a" id="176a" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">encodeURI()</code> — Encodes a URI into UTF-8</li>
<li name="6720" id="6720" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">encodeURIComponent()</code> — Same but for URI components</li>
<li name="e97b" id="e97b" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">eval()</code> — Evaluates JavaScript code represented as a
string</li>
<li name="390b" id="390b" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">isFinite()</code> — Determines whether a passed value is a
finite number</li>
<li name="5d46" id="5d46" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">isNaN()</code> — Determines whether a value is NaN or not</li>
<li name="f668" id="f668" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">Number()</code> —- Returns a number converted from its argument
</li>
<li name="a5ff" id="a5ff" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">parseFloat()</code> — Parses an argument and returns a
floating-point number</li>
<li name="a666" id="a666" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">parseInt()</code> — Parses its argument and returns an integer
</li>
</ul>
<h3 name="a649" id="a649" class="graf graf--h3 graf-after--li">JavaScript Loops</h3>
<p name="6cff" id="6cff" class="graf graf--p graf-after--h3">Loops are part of most programming languages.
They allow you to execute blocks of code desired number of times with different values:</p>
<p name="01bf" id="01bf" class="graf graf--p graf-after--p">for (before loop; condition <strong
class="markup--strong markup--p-strong">for</strong> loop; execute after loop) {</p>
<p name="5eb2" id="5eb2" class="graf graf--p graf-after--p">// what to do during the loop</p>
<p name="e346" id="e346" class="graf graf--p graf-after--p">}</p>
<p name="ff25" id="ff25" class="graf graf--p graf-after--p">You have several parameters to create loops:
</p>
<ul class="postList">
<li name="ff62" id="ff62" class="graf graf--li graf-after--p"><code
class="markup--code markup--li-code">for</code> — The most common way to create a loop in JavaScript
</li>
<li name="7ad1" id="7ad1" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">while</code> — Sets up conditions under which a loop executes
</li>
<li name="c2f4" id="c2f4" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">do while</code> — Similar to the <code
class="markup--code markup--li-code">while</code> loop but it executes at least once and performs a
check at the end to see if the condition is met to execute again</li>
<li name="7157" id="7157" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">break</code> —Used to stop and exit the cycle at certain
conditions</li>
<li name="f5c0" id="f5c0" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">continue</code> — Skip parts of the cycle if certain conditions
are met</li>
</ul>
<h3 name="ba4b" id="ba4b" class="graf graf--h3 graf-after--li">If — Else Statements</h3>
<p name="d781" id="d781" class="graf graf--p graf-after--h3">These types of statements are easy to
understand. Using them, you can set conditions for when your code is executed. If certain conditions
apply, something is done, if not — something else is executed.</p>
<p name="c7b4" id="c7b4" class="graf graf--p graf-after--p">if (condition) {</p>
<p name="a1cb" id="a1cb" class="graf graf--p graf-after--p">// what to do if condition is met</p>
<p name="6c77" id="6c77" class="graf graf--p graf-after--p">} <strong
class="markup--strong markup--p-strong">else</strong> {</p>
<p name="99e2" id="99e2" class="graf graf--p graf-after--p">// what to do if condition is not met</p>
<p name="5fed" id="5fed" class="graf graf--p graf-after--p">}</p>
<p name="2f4c" id="2f4c" class="graf graf--p graf-after--p">A similar concept to <code
class="markup--code markup--p-code">if else</code> is the <code
class="markup--code markup--p-code">switch</code> statement. However, using the switch you select one
of several code blocks to execute.</p>
<h3 name="f11b" id="f11b" class="graf graf--h3 graf-after--p">Strings</h3>
<p name="749a" id="749a" class="graf graf--p graf-after--h3">Strings are what JavaScript calls to text
that does not perform a function but can appear on the screen.</p>
<p name="e87c" id="e87c" class="graf graf--p graf-after--p">var person = “John Doe”;</p>
<p name="c838" id="c838" class="graf graf--p graf-after--p">In this case, <code
class="markup--code markup--p-code">John Doe</code> is the string.</p>
<h3 name="1169" id="1169" class="graf graf--h3 graf-after--p">Escape Characters</h3>
<p name="19ce" id="19ce" class="graf graf--p graf-after--h3">In JavaScript, strings are marked with single
or double-quotes. If you want to use quotation marks in a string, you need to use special characters:
</p>
<ul class="postList">
<li name="b4b1" id="b4b1" class="graf graf--li graf-after--p"><code
class="markup--code markup--li-code">\'</code> — Single quote</li>
<li name="3b22" id="3b22" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\"</code> — Double quote</li>
</ul>
<p name="d76f" id="d76f" class="graf graf--p graf-after--li">Aside from that you also have additional
escape characters:</p>
<ul class="postList">
<li name="b412" id="b412" class="graf graf--li graf-after--p"><code
class="markup--code markup--li-code">\\</code> — Backslash</li>
<li name="1592" id="1592" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\b</code> — Backspace</li>
<li name="3a72" id="3a72" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\f</code> — Form feed</li>
<li name="145a" id="145a" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\n</code> — New line</li>
<li name="1416" id="1416" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\r</code> — Carriage return</li>
<li name="95d4" id="95d4" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\t</code> — Horizontal tabulator</li>
<li name="d962" id="d962" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\v</code> — Vertical tabulator</li>
</ul>
<h3 name="8f75" id="8f75" class="graf graf--h3 graf-after--li">String Methods</h3>
<p name="733b" id="733b" class="graf graf--p graf-after--h3">There are many different ways to work with
strings:</p>
<ul class="postList">
<li name="2021" id="2021" class="graf graf--li graf-after--p"><code
class="markup--code markup--li-code">charAt()</code> — Returns a character at a specified position
inside a string</li>
<li name="d3e5" id="d3e5" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">charCodeAt()</code> — Gives you the Unicode of a character at
that position</li>
<li name="fdd1" id="fdd1" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">concat()</code> — Concatenates (joins) two or more strings into
one</li>
<li name="009c" id="009c" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">fromCharCode()</code> — Returns a string created from the
specified sequence of UTF-16 code units</li>
<li name="7ed3" id="7ed3" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">indexOf()</code> — Provides the position of the first
occurrence of a specified text within a string</li>
<li name="2937" id="2937" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">lastIndexOf()</code> — Same as <code
class="markup--code markup--li-code">indexOf()</code> but with the last occurrence, searching
backward</li>
<li name="142d" id="142d" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">match()</code> — Retrieves the matches of a string against a
search pattern</li>
<li name="6c18" id="6c18" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">replace()</code> — Find and replace specified text in a string
</li>
<li name="e279" id="e279" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">search()</code> — Executes a search for a matching text and
returns its position</li>
<li name="6bcd" id="6bcd" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">slice()</code> — Extracts a section of a string and returns it
as a new string</li>
<li name="e4ee" id="e4ee" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">split()</code> — Splits a string object into an array of
strings at a specified position</li>
<li name="3a27" id="3a27" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">substr()</code> — Similar to <code
class="markup--code markup--li-code">slice()</code> but extracts a substring depending on a
specified number of characters</li>
<li name="3d14" id="3d14" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">substring()</code> — Also similar to <code
class="markup--code markup--li-code">slice()</code> but can’t accept negative indices</li>
<li name="fa33" id="fa33" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">toLowerCase()</code> — Convert strings to lower case</li>
<li name="3485" id="3485" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">toUpperCase()</code> — Convert strings to upper case</li>
<li name="4f96" id="4f96" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">valueOf()</code> — Returns the primitive value (that has no
properties or methods) of a string object</li>
</ul>
<h3 name="cde1" id="cde1" class="graf graf--h3 graf-after--li">Regular Expression Syntax</h3>
<p name="85dc" id="85dc" class="graf graf--p graf-after--h3">Regular expressions are search patterns used
to match character combinations in strings. The search pattern can be used for text search and text to
replace operations.</p>
<h3 name="1a51" id="1a51" class="graf graf--h3 graf-after--p">Pattern Modifiers</h3>
<ul class="postList">
<li name="bb29" id="bb29" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">e</code> — Evaluate replacement</li>
<li name="b6b8" id="b6b8" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">i</code> — Perform case-insensitive matching</li>
<li name="4f50" id="4f50" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">g</code> — Perform global matching</li>
<li name="4add" id="4add" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">m</code> — Perform multiple line matching</li>
<li name="a073" id="a073" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">s</code> — Treat strings as a single line</li>
<li name="482b" id="482b" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">x</code> — Allow comments and whitespace in the pattern</li>
<li name="f6ad" id="f6ad" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">U</code> — Ungreedy pattern</li>
</ul>
<h3 name="f430" id="f430" class="graf graf--h3 graf-after--li">Brackets</h3>
<ul class="postList">
<li name="aae1" id="aae1" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">[abc]</code> — Find any of the characters between the brackets
</li>
<li name="e048" id="e048" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">[^abc]</code> — Find any character which is not in the brackets
</li>
<li name="f9b5" id="f9b5" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">[0-9]</code> — Used to find any digit from 0 to 9</li>
<li name="ac71" id="ac71" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">[A-z]</code> — Find any character from uppercase A to lowercase
z</li>
<li name="6fce" id="6fce" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">(a|b|c)</code> — Find any of the alternatives separated with
<code class="markup--code markup--li-code">|</code></li>
</ul>
<h3 name="ef6e" id="ef6e" class="graf graf--h3 graf-after--li">Metacharacters</h3>
<ul class="postList">
<li name="dcd6" id="dcd6" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">.</code> — Find a single character, except newline or line
terminator</li>
<li name="e944" id="e944" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\w</code> — Word character</li>
<li name="c4bf" id="c4bf" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\W</code> — Non-word character</li>
<li name="7b81" id="7b81" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\d</code> — A digit</li>
<li name="a533" id="a533" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\D</code> — A non-digit character</li>
<li name="1fcc" id="1fcc" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\s</code> — Whitespace character</li>
<li name="374c" id="374c" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\S</code> — Non-whitespace character</li>
<li name="72d0" id="72d0" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\b</code> — Find a match at the beginning/end of a word</li>
<li name="2d38" id="2d38" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\B</code> — A match not at the beginning/end of a word</li>
<li name="859b" id="859b" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\0</code> — NUL character</li>
<li name="df4d" id="df4d" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\n</code> — A new line character</li>
<li name="5acd" id="5acd" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\f</code> — Form feed character</li>
<li name="833f" id="833f" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\r</code> — Carriage return character</li>
<li name="4f31" id="4f31" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\t</code> — Tab character</li>
<li name="e618" id="e618" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\v</code> — Vertical tab character</li>
<li name="dcfc" id="dcfc" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\xxx</code> — The character specified by an octal number xxx
</li>
<li name="cf5e" id="cf5e" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\xdd</code> — Character specified by a hexadecimal number dd
</li>
<li name="978f" id="978f" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">\uxxxx</code> — The Unicode character specified by a
hexadecimal number XXXX</li>
</ul>
<h3 name="ab62" id="ab62" class="graf graf--h3 graf-after--li">Quantifiers</h3>
<ul class="postList">
<li name="e4cf" id="e4cf" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">n+</code> — Matches any string that contains at least one n
</li>
<li name="be07" id="be07" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">n*</code> — Any string that contains zero or more occurrences
of n</li>
<li name="4a93" id="4a93" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">n?</code> — A string that contains zero or one occurrence of n
</li>
<li name="91f0" id="91f0" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">n{X}</code> — String that contains a sequence of X n’s</li>
<li name="097b" id="097b" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">n{X,Y}</code> — Strings that contain a sequence of X to Y n’s
</li>
<li name="e9f2" id="e9f2" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">n{X,}</code> — Matches any string that contains a sequence of
at least X n’s</li>
<li name="15b3" id="15b3" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">n$</code> — Any string with n at the end of it</li>
<li name="5fc9" id="5fc9" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">^n</code> — String with n at the beginning of it</li>
<li name="2b42" id="2b42" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">?=n</code> — Any string that is followed by a specific string n
</li>
<li name="6ffa" id="6ffa" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">?!n</code> — String that is not followed by a specific string
ni</li>
</ul>
<h3 name="20fa" id="20fa" class="graf graf--h3 graf-after--li">Numbers and Math</h3>
<p name="54b2" id="54b2" class="graf graf--p graf-after--h3">In JavaScript, you can also work with
numbers, constants and perform mathematical functions.</p>
<h3 name="2440" id="2440" class="graf graf--h3 graf-after--p">Number Properties</h3>
<ul class="postList">
<li name="3554" id="3554" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">MAX_VALUE</code> — The maximum numeric value representable in
JavaScript</li>
<li name="c55d" id="c55d" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">MIN_VALUE</code> — Smallest positive numeric value
representable in JavaScript</li>
<li name="49e0" id="49e0" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">NaN</code> — The “Not-a-Number” value</li>
<li name="3024" id="3024" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">NEGATIVE_INFINITY</code> — The negative Infinity value</li>
<li name="0bf4" id="0bf4" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">POSITIVE_INFINITY</code> — Positive Infinity value</li>
</ul>
<h3 name="7d65" id="7d65" class="graf graf--h3 graf-after--li">Number Methods</h3>
<ul class="postList">
<li name="9478" id="9478" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">toExponential()</code> — Returns the string with a rounded
number written as exponential notation</li>
<li name="2ad0" id="2ad0" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">toFixed()</code> — Returns the string of a number with a
specified number of decimals</li>
<li name="d464" id="d464" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">toPrecision()</code> — String of a number written with a
specified length</li>
<li name="2244" id="2244" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">toString()</code> — Returns a number as a string</li>
<li name="bc1e" id="bc1e" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">valueOf()</code> — Returns a number as a number</li>
</ul>
<h3 name="08ba" id="08ba" class="graf graf--h3 graf-after--li">Math Properties</h3>
<ul class="postList">
<li name="9f68" id="9f68" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">E</code> — Euler’s number</li>
<li name="a4df" id="a4df" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">LN2</code> — The natural logarithm of 2</li>
<li name="0f06" id="0f06" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">LN10</code> — Natural logarithm of 10</li>
<li name="1a92" id="1a92" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">LOG2E</code> — Base 2 logarithm of E</li>
<li name="42e7" id="42e7" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">LOG10E</code> — Base 10 logarithm of E</li>
<li name="1fbe" id="1fbe" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">PI</code> — The number PI</li>
<li name="2a56" id="2a56" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">SQRT1_2</code> — Square root of 1/2</li>
<li name="aab4" id="aab4" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">SQRT2</code> — The square root of 2</li>
</ul>
<h3 name="75f9" id="75f9" class="graf graf--h3 graf-after--li">Math Methods</h3>
<ul class="postList">
<li name="8836" id="8836" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">abs(x)</code> — Returns the absolute (positive) value of x</li>
<li name="ddb9" id="ddb9" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">acos(x)</code> — The arccosine of x, in radians</li>
<li name="a0c3" id="a0c3" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">asin(x)</code> — Arcsine of x, in radians</li>
<li name="c2ca" id="c2ca" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">atan(x)</code> — The arctangent of x as a numeric value</li>
<li name="8b93" id="8b93" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">atan2(y,x)</code> — Arctangent of the quotient of its arguments
</li>
<li name="b103" id="b103" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">ceil(x)</code> — Value of x rounded up to its nearest integer
</li>
<li name="c68a" id="c68a" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">cos(x)</code> — The cosine of x (x is in radians)</li>
<li name="d480" id="d480" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">exp(x)</code> — Value of Ex</li>
<li name="2954" id="2954" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">floor(x)</code> — The value of x rounded down to its nearest
integer</li>
<li name="ff4d" id="ff4d" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">log(x)</code> — The natural logarithm (base E) of x</li>
<li name="b6a9" id="b6a9" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">max(x,y,z,...,n)</code> — Returns the number with the highest
value</li>
<li name="dfb0" id="dfb0" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">min(x,y,z,...,n)</code> — Same for the number with the lowest
value</li>
<li name="a6f1" id="a6f1" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">pow(x,y)</code> — X to the power of y</li>
<li name="8851" id="8851" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">random()</code> — Returns a random number between 0 and 1</li>
<li name="d32e" id="d32e" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">round(x)</code> — The value of x rounded to its nearest integer
</li>
<li name="fe9a" id="fe9a" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">sin(x)</code> — The sine of x (x is in radians)</li>
<li name="c244" id="c244" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">sqrt(x)</code> — Square root of x</li>
<li name="b5ef" id="b5ef" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">tan(x)</code> — The tangent of an angle</li>
</ul>
<h3 name="81f5" id="81f5" class="graf graf--h3 graf-after--li">Dealing with Dates in JavaScript</h3>
<p name="45cb" id="45cb" class="graf graf--p graf-after--h3">You can also work with and modify dates and
time with JavaScript. This is the next chapter in the JavaScript cheat sheet.</p>
<h3 name="9b09" id="9b09" class="graf graf--h3 graf-after--p">Setting Dates</h3>
<ul class="postList">
<li name="b187" id="b187" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">Date()</code> — Creates a new date object with the current date
and time</li>
<li name="42f8" id="42f8" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">Date(2017, 5, 21, 3, 23, 10, 0)</code> — Create a custom date
object. The numbers represent a year, month, day, hour, minutes, seconds, milliseconds. You can omit
anything you want except for a year and month.</li>
<li name="4e80" id="4e80" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">Date("2017-06-23")</code> — Date declaration as a
string</li>
</ul>
<h3 name="b746" id="b746" class="graf graf--h3 graf-after--li">Pulling Date and Time Values</h3>
<ul class="postList">
<li name="465e" id="465e" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">getDate()</code> — Get the day of the month as a number (1-31)
</li>
<li name="1b08" id="1b08" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">getDay()</code> — The weekday as a number (0-6)</li>
<li name="6d9e" id="6d9e" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">getFullYear()</code> — Year as a four-digit number (yyyy)</li>
<li name="a216" id="a216" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">getHours()</code> — Get the hour (0-23)</li>
<li name="388a" id="388a" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">getMilliseconds()</code> — The millisecond (0-999)</li>
<li name="a97f" id="a97f" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">getMinutes()</code> — Get the minute (0-59)</li>
<li name="2427" id="2427" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">getMonth()</code> — Month as a number (0-11)</li>
<li name="b964" id="b964" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">getSeconds()</code> — Get the second (0-59)</li>
<li name="505d" id="505d" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">getTime()</code> — Get the milliseconds since January 1, 1970
</li>
<li name="7c14" id="7c14" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">getUTCDate()</code> — The day (date) of the month in the
specified date according to universal time (also available for day, month, full year, hours, minutes
etc.)</li>
<li name="d6b6" id="d6b6" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">parse</code> — Parses a string representation of a date and
returns the number of milliseconds since January 1, 1970</li>
</ul>
<h3 name="ec7c" id="ec7c" class="graf graf--h3 graf-after--li">Set Part of a Date</h3>
<ul class="postList">
<li name="9a97" id="9a97" class="graf graf--li graf-after--h3"><code
class="markup--code markup--li-code">setDate()</code> — Set the day as a number (1-31)</li>
<li name="d4f0" id="d4f0" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">setFullYear()</code> — Sets the year (optionally month and day)
</li>
<li name="1a45" id="1a45" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">setHours()</code> — Set the hour (0-23)</li>
<li name="8020" id="8020" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">setMilliseconds()</code> — Set milliseconds (0-999)</li>
<li name="7feb" id="7feb" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">setMinutes()</code> — Sets the minutes (0-59)</li>
<li name="d7ca" id="d7ca" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">setMonth()</code> — Set the month (0-11)</li>
<li name="795d" id="795d" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">setSeconds()</code> — Sets the seconds (0-59)</li>
<li name="1d7f" id="1d7f" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">setTime()</code> — Set the time (milliseconds since January 1,
1970)</li>
<li name="78e1" id="78e1" class="graf graf--li graf-after--li"><code
class="markup--code markup--li-code">setUTCDate()</code> — Sets the day of the month for a specified
date according to universal time (also available for day, month, full year, hours, minutes etc.)</li>