Javascript Basics
Including JavaScript in an HTML Page


<script type="text/javascript">

 //JS code goes here

</script>


Call an External JavaScript File


<script src="myscript.js"></script><code></code>


Including Comments

Single line comments - // Comment

Multi-line comments - /* comment here */



Variables
var, const, let

var — The most common variable. Can be reassigned but only accessed

within a function. Variables defined with var move to the top when

code is executed.

const — Can not be reassigned and not accessible before they appear

within the code.

let — Similar to const, however, let variable can be reassigned but

not re-declared.


 

Data Types
Numbers — var age = 23

Variables — var x

Text (strings) — var a = "init"

Operations — var b = 1 + 2 + 3

True or fase statements — var c = true

Constant numbers — const PI = 3.14

Objects — var name = {firstName:"John", lastName:”Doe"}


Objects
var person = {

 firstName:"John",

 lastName:"Doe",

 age:20,

 nationality:"American"

};