JavaScript Basic Syntax

Hello world (Printing & Commenting)

// this is a comment
console.log("Hello world")
/*
 * This is a multiline comment
*/
console.log(`This is an variable ${X} in the log  `)

Variables

var variable = "I can change and im hoisted" // Variable with hoisting
let myName = "I can change" // Variable with blockscope 
const myConst = "I wont change"

Const

It does not define a constant value. It defines a constant reference to a value.

Can NOT:

• Reassign a constant value
• Reassign a constant array
• Reassign a constant object

But you CAN:

• Change the elements of constant array
• Change the properties of constant object

Scope

Global scope

let carName = "Volvo";  
// code here can use carName  
  
function myFunction() {  
// code here can also use carName  
}

Block scope

let,const: Variables declared inside a { } block cannot be accessed from outside the block:
var Variables declared inside a { } block can be accessed from outside the block.

{  
  let x = 2;  
}  
// x can NOT be used here
{  
  var x = 2;  
}  
// x CAN be used here

Operators

• ??
• ?. safe call
• !!
• ...object Object spread

Data Types

Number

BigInt

String

Boolean

Undefined

Object

Null

Null vs Undefined

Symbol

Data Structures

Sets

Functions

• similarities to Kotlin Syntax
• assign variables

function myFunction(param,param,...theRestOfParams){
	return param * param
}

Anonymous

Hoisting

Control Flow

• if
  • ternary
• switch
• for

Nullability

Relates to

References