Javascript - Array includes() method

You can check if an element exists in an Array using this method.

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Description

You can check if an element exists in an Array using this method.

It will return a Boolean value based on whether or not the element passed to it is a part of the array it is used on.

Demo

['XML', 'Screen', 'carrot'].includes('XML');    //true 
['XML', 'Screen', 'carrot'].includes('Keyboard');   //false

The above example is equivalent to: 

['XML', 'Screen', 'carrot'].indexOf('XML') >= 0;    //true 
['XML', 'Screen', 'carrot'].indexOf('Keyboard') >= 0;   //false

includes method regards all value NaN (Not a Number) as equal. 

const arr = [NaN]; 
arr.includes(NaN);              // true 
arr.indexOf(NaN);               // -1

indexOf cannot be used to check for NaN values inside an array, but the includes method allows us to check if a NaN value exists inside an array.