JS Types

• numbers, booleans, string, undefined, null, symbol, object
• typeof null gives an obejct (this is a mistake)
• Symbols allow object properties to be unique
• undefined is the absence of a definition, null is absence of a value
• arrays and functions are objects (underneath the hood)
• 2 distinctions
  • primitive: data that only represents a single value
    • number
    • boolean
    • string
    • undefined
    • null
    • symbol
  • non-primitive: doesn't contain value directly, it has a reference to where object is held
    • object
    • array
    • function
• primitives get complicated because they can be used like objects, for example: true.toString() calls a wrapper object like this: Boolean(true) before executing code

Array.isArray()

• JS does this to arrays:

var array = ['1', '2', '3'];

var array = {
	0: '1',
	1: '2',
	2: '3'
}

• Array.isArray allows us to check if object is an array

Pass by value vs reference

• primitive types are passed by value
• non-prmitive types are passed by reference
• pass by value basically means we copy the value and place it somehwere else in memory
• pass by reference allows us to save a lot of memory space

Type Coercion

JTS: Dynamic vs Static Typing

JTS: Weakly vs Strongly Typed

JTS: Static Typing in JS