Check if an element is present in an array [duplicate]

Question

The function I am using now to check this is the following:

function inArray(needle,haystack) {     var count=haystack.length;     for(var i=0;i<count;i++)     {         if(haystack[i]===needle){return true;}     }     return false; } 

It works. What I'm looking for is whether there is a better way of doing this.

Answer 1

ECMAScript 2016 incorporates an includes() method for arrays that specifically solves the problem, and so is now the preferred method.

[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) 

As of JULY 2018, this has been implemented in almost all major browsers, if you need to support an older browser a polyfill is available.

Edit: Note that this returns false if the item in the array is an object. This is because similar objects are two different objects in JavaScript.

Answer 2

Code:

function isInArray(value, array) {   return array.indexOf(value) > -1; } 

Execution:

isInArray(1, [1,2,3]); // true 

Update (2017):

In modern browsers which follow the ECMAScript 2016 (ES7) standard, you can use the function Array.prototype.includes, which makes it way more easier to check if an item is present in an array:

const array = [1, 2, 3]; const value = 1; const isInArray = array.includes(value); console.log(isInArray); // true