Complete key errors, mandatory and interpret tasks for Sprint 2

Author: MouawiaElkhalifa

Sprint-2/1-key-errors/0.js

@@ -1,6 +1,11 @@
 // Predict and explain first...
 //  =============> write your prediction here
 
+// Prediction:
+// The code will throw an error because `str` is declared twice:
+// once as the function parameter and again with `let str` inside the function.
+// JavaScript does not allow redeclaring the same identifier in the same scope.
+
 // call the function capitalise with a string input
 // interpret the error message and figure out why an error is occurring
 
@@ -10,4 +15,20 @@ function capitalise(str) {
 }
 
 // =============> write your explanation here
+
+// Explanation:
+// When the file runs, JavaScript gives a SyntaxError like:
+// "Identifier 'str' has already been declared".
+// This happens because `str` already exists as a parameter, so `let str` tries
+// to redeclare it in the same scope. To fix it, we should not redeclare `str`.
+// Instead, we can create a new variable or just return the new string.
+
 // =============> write your new code here
+
+function capitalise(str) {
+  str = `${str[0].toUpperCase()}${str.slice(1)}`;
+  return str;
+}
+
+console.log(capitalise("hello")); // Hello
+

Sprint-2/1-key-errors/1.js

@@ -3,6 +3,14 @@
 // Why will an error occur when this program runs?
 // =============> write your prediction here
 
+// Prediction:
+// An error will occur because `decimalNumber` is declared twice.
+// It is first declared as a function parameter and then declared again
+// inside the function using `const decimalNumber = 0.5;`.
+// JavaScript does not allow redeclaring the same variable in the same scope.
+// Also, `console.log(decimalNumber);` is outside the function,
+// so `decimalNumber` is not defined in the global scope.
+
 // Try playing computer with the example to work out what is going on
 
 function convertToPercentage(decimalNumber) {
@@ -16,5 +24,21 @@ console.log(decimalNumber);
 
 // =============> write your explanation here
 
+// Explanation:
+// The parameter `decimalNumber` is already defined in the function.
+// Declaring `const decimalNumber = 0.5;` again causes a SyntaxError:
+// "Identifier 'decimalNumber' has already been declared".
+// Additionally, `console.log(decimalNumber);` causes a ReferenceError
+// because `decimalNumber` only exists inside the function and
+// cannot be accessed outside of it.
+
 // Finally, correct the code to fix the problem
 // =============> write your new code here
+
+function convertToPercentage(decimalNumber) {
+  const percentage = `${decimalNumber * 100}%`;
+  return percentage;
+}
+
+const result = convertToPercentage(0.5);
+console.log(result); // 50%

Sprint-2/1-key-errors/2.js

@@ -1,20 +1,46 @@
-
 // Predict and explain first BEFORE you run any code...
 
 // this function should square any number but instead we're going to get an error
 
 // =============> write your prediction of the error here
 
+// Prediction:
+// An error will occur because `3` is not a valid parameter name.
+// Function parameters must be variable names, not numbers.
+// JavaScript will throw a SyntaxError before running the program.
+
 function square(3) {
     return num * num;
 }
 
 // =============> write the error message here
 
+// Error message:
+// SyntaxError: Unexpected number
+
 // =============> explain this error message here
 
+// Explanation:
+// The error occurs because `3` is used as the function parameter.
+// In JavaScript, function parameters must be identifiers (variable names).
+// A number cannot be used as a parameter name.
+// Because of this invalid syntax, JavaScript throws a SyntaxError
+// before the program can run.
+// Additionally, the variable `num` is used inside the function
+// but is not defined, which would cause another error
+// if the syntax error did not occur first.
+
 // Finally, correct the code to fix the problem
 
 // =============> write your new code here
 
+function square(num) {
+    return num * num;
+}
+
+console.log(square(3)); // 9
+
+
+
+
 

Sprint-2/2-mandatory-debug/0.js

@@ -2,13 +2,41 @@
 
 // =============> write your prediction here
 
+// Prediction:
+// The program will print 320,
+// but it will also print "undefined" in the sentence.
+// This happens because the function uses console.log()
+// instead of returning a value.
+// If a function does not return anything,
+// JavaScript automatically returns undefined.
+
 function multiply(a, b) {
   console.log(a * b);
 }
 
 console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);
 
+
 // =============> write your explanation here
 
+// Explanation:
+// The function multiply(a, b) prints the result using console.log(),
+// but it does not return the result.
+// When multiply(10, 32) is used inside the template string,
+// JavaScript expects a returned value.
+// Because nothing is returned, the value becomes undefined.
+// That is why the output shows:
+//
+// 320
+// The result of multiplying 10 and 32 is undefined
+
+
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+
+function multiply(a, b) {
+  return a * b;
+}
+
+console.log(`The result of multiplying 10 and 32 is ${multiply(10, 32)}`);//320
+

Sprint-2/2-mandatory-debug/1.js

@@ -1,13 +1,35 @@
 // Predict and explain first...
 //  =============> write your prediction here
 
+// Prediction:
+// The program will print "The sum of 10 and 32 is undefined".
+// This happens because the return statement is written incorrectly.
+// JavaScript stops executing a function immediately after "return".
+// Since nothing is returned, the function returns undefined.
+
 function sum(a, b) {
   return;
   a + b;
 }
 
 console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);
 
+
 // =============> write your explanation here
+
+// Explanation:
+// In JavaScript, when "return" is written on its own line,
+// the function stops immediately and returns undefined.
+// The line "a + b;" is never executed.
+// That is why sum(10, 32) becomes undefined.
+// The issue is caused by the line break after return.
+
+
 // Finally, correct the code to fix the problem
 //  =============> write your new code here
+
+function sum(a, b) {
+  return a + b;
+}
+
+console.log(`The sum of 10 and 32 is ${sum(10, 32)}`);//32

Sprint-2/2-mandatory-debug/2.js

@@ -3,6 +3,12 @@
 // Predict the output of the following code:
 // =============> Write your prediction here
 
+// Prediction:
+// The function will always return "3".
+// Even though we pass 42, 105, and 806 into the function,
+// it will ignore those values and use the global variable `num = 103`.
+// Therefore, every line will print 3 as the last digit.
+
 const num = 103;
 
 function getLastDigit() {
@@ -13,12 +19,43 @@ console.log(`The last digit of 42 is ${getLastDigit(42)}`);
 console.log(`The last digit of 105 is ${getLastDigit(105)}`);
 console.log(`The last digit of 806 is ${getLastDigit(806)}`);
 
+
 // Now run the code and compare the output to your prediction
 // =============> write the output here
+
+// Output:
+// The last digit of 42 is 3
+// The last digit of 105 is 3
+// The last digit of 806 is 3
+
+
 // Explain why the output is the way it is
 // =============> write your explanation here
+
+// Explanation:
+// The function getLastDigit does not accept a parameter.
+// Because of that, it ignores the values passed inside the parentheses.
+// Instead, it always uses the global constant `num`, which is 103.
+// The function converts 103 to a string and takes the last character,
+// which is "3". That is why every output is 3.
+
+
 // Finally, correct the code to fix the problem
 // =============> write your new code here
 
+function getLastDigit(number) {
+  return number.toString().slice(-1);
+}
+
+console.log(`The last digit of 42 is ${getLastDigit(42)}`);//2
+console.log(`The last digit of 105 is ${getLastDigit(105)}`);//5
+console.log(`The last digit of 806 is ${getLastDigit(806)}`);//6
+
+
 // This program should tell the user the last digit of each number.
 // Explain why getLastDigit is not working properly - correct the problem
+
+// The function was not working properly because it did not use a parameter.
+// It was hard-coded to use the global variable `num` instead of the value
+// passed into the function. By adding a parameter (number),
+// the function now works correctly for any input.

Sprint-2/3-mandatory-implement/1-bmi.js

@@ -16,4 +16,7 @@
 
 function calculateBMI(weight, height) {
     // return the BMI of someone based off their weight and height
-}
+let bmi =weight/(height*height);
+return bmi.toFixed(1)}
+console.log(calculateBMI(88, 1.78));//27.8
+

Sprint-2/3-mandatory-implement/2-cases.js

@@ -14,3 +14,11 @@
 // You will need to come up with an appropriate name for the function
 // Use the MDN string documentation to help you find a solution
 // This might help https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String/toUpperCase
+
+function toUpperSnakeCase(str) {
+  return str.replaceAll(" ", "_").toUpperCase();
+}
+
+console.log(toUpperSnakeCase("hello there"));        // "HELLO_THERE"
+console.log(toUpperSnakeCase("lord of the rings"));  // "LORD_OF_THE_RINGS"
+

Sprint-2/3-mandatory-implement/3-to-pounds.js

@@ -1,6 +1,31 @@
 // In Sprint-1, there is a program written in interpret/to-pounds.js
-
 // You will need to take this code and turn it into a reusable block of code.
 // You will need to declare a function called toPounds with an appropriately named parameter.
-
 // You should call this function a number of times to check it works for different inputs
+
+function toPounds(penceString) {
+  const penceStringWithoutTrailingP = penceString.substring(
+    0,
+    penceString.length - 1
+  );
+
+  const paddedPenceNumberString = penceStringWithoutTrailingP.padStart(3, "0");
+
+  const pounds = paddedPenceNumberString.substring(
+    0,
+    paddedPenceNumberString.length - 2
+  );
+
+  const pence = paddedPenceNumberString
+    .substring(paddedPenceNumberString.length - 2)
+    .padEnd(2, "0");
+
+  return `£${pounds}.${pence}`;
+}
+
+// Call the function a number of times to check it works for different inputs
+console.log(toPounds("399p"));  // £3.99
+console.log(toPounds("5p"));    // £0.05
+console.log(toPounds("45p"));   // £0.45
+console.log(toPounds("120p"));  // £1.20
+console.log(toPounds("0p"));    // £0.00

Sprint-2/4-mandatory-interpret/time-format.js

@@ -11,24 +11,29 @@ function formatTimeDisplay(seconds) {
   return `${pad(totalHours)}:${pad(remainingMinutes)}:${pad(remainingSeconds)}`;
 }
 
+// Calling the function with 61 as the argument
+console.log(formatTimeDisplay(61)); 
+
+
+
 // You will need to play computer with this example - use the Python Visualiser https://pythontutor.com/visualize.html#mode=edit
 // to help you answer these questions
 
 // Questions
 
 // a) When formatTimeDisplay is called how many times will pad be called?
-// =============> write your answer here
+// =============> pad will be called 3 times.
 
 // Call formatTimeDisplay with an input of 61, now answer the following:
 
 // b) What is the value assigned to num when pad is called for the first time?
-// =============> write your answer here
+// =============> The value is 0.
 
 // c) What is the return value of pad is called for the first time?
-// =============> write your answer here
+// =============> The return value is "00".
 
 // d) What is the value assigned to num when pad is called for the last time in this program?  Explain your answer
-// =============> write your answer here
+// =============> The value is 1 because 61 % 60 leaves 1 second remaining.
 
 // e) What is the return value assigned to num when pad is called for the last time in this program?  Explain your answer
-// =============> write your answer here
+// =============> The return value is "01" because return num.toString().padStart(2, "0") formats 1 into "01".