type of javascript

 What value it has 	 			What the output shows you 
 						when you write |console.log(typeof(variable);
Undefined:						"undefined"
Null:							"object"
Boolean:						"boolean"
Number:							"number"
String:							"string"
Function object:				"function"
E4X XML object:					"xml"
E4X XMLList object:				"xml"
NodeList						"Nodelist [more data]"
HTMLCollection					"HTMLCollection(1) [more data]"// get type of variable

var number = 1
var string = 'hello world'
var dict = {a: 1, b: 2, c: 3}

console.log(typeof number) // number
console.log(typeof string) // string
console.log(typeof dict)   // object> typeof "foo"
> typeof true
> typeof 42

if(typeof bar === 'number') {
}//retourne le type de la variable

let number = 1;
let string = "bonjour";
let bool = true;
let dict = { a: 1, b:2 };

console.log(typeof(number));//renvoie Number
console.log(typeof(string));//renvoie String
console.log(typeof(bool));//renvoie Boolean
console.log(typeof(dict));//renvoie Object

//cas spécial

console.log(typeof(NaN));//NaN = Not A Number renvoie Number//typeof() will return the type of value in it's parameters.
//some examples of types: undefined, NaN, number, string, object, array

//example of a practical usage
if (typeof(value) !== "undefined") {//asuming value is already set
  	//execute code
}if (typeof i != "number") {
    console.log('This is not number');

Also in JavaScript: