check if something is in array javascript code example

Example 1: check value exist in array javascript

[1, 2, 3].includes(2);     // true
[1, 2, 3].includes(4);     // false
[1, 2, 3].includes(1, 2);  // false (second parameter is the index position in this array at which to begin searching)

Example 2: how to check if item is in list js

var myList=["a", "b", "c"];
mylist.includes("d")//returns true or false

Example 3: javascript array contains

var fruits = ["Banana", "Orange", "Apple", "Mango"];
var n = fruits.includes("Mango");

Example 4: javascript check if in array

var extensions = ["image/jpeg","image/png","image/gif"];          
if(extensions.indexOf("myfiletype") === -1){
	alert("Image must be .png, .jpg or .gif");
}