find-if-an-item-is-in-a-javascript-array

http://stackoverflow.com/questions/143847/best-way-to-find-if-an-item-is-in-a-javascript-array

153

This question already has an answer here:

How do I check if an array includes an object in JavaScript? 33 answers

What is the best way to find if an object is in an array?

This is the best way I know:

function include(arr, obj) {
    for(var i=0; i<arr.length; i++) {
        if (arr[i] == obj) return true;
    }
}

include([1,2,3,4], 3); // true
include([1,2,3,4], 6); // undefined

edited Jan 6 at 21:05

Gothdo

18.4k104879

asked Sep 27 '08 at 15:41

zimbatm

3,60041411

marked as duplicate by Gothdo javascript Jan 6 at 21:04

This question has been asked before and already has an answer. If those answers do not fully address your question, please ask a new question.

See: stackoverflow.com/a/25765186/1320932 – dr.dimitru Sep 10 '14 at 12:18

2 things: 1.) 'include' is a really bad name for a function that does not modify the state of anything. It's especially bad for a function that simply returns a boolean. 2.) You need to add "return(false);" before the end of the function. – Aquarelle May 12 '15 at 0:57

as of ECMAScript 2016, you can use Array.prototype.includes function: myArray.includes(3); // true – mhdJun 15 '16 at 13:25

In ES6 you can do something like arr.find(lamda function) , example: [1, 2, 3,4,5].find(x => x == 3). if element is found it is returned else undefined is returned – allsyed Jul 29 '16 at 10:26

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8 Answers

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up vote565down voteaccepted

function include(arr,obj) {
    return (arr.indexOf(obj) != -1);
}

EDIT: This will not work on IE6, 7 or 8 though. The best workaround is to define it yourself if it's not present:

Mozilla's (ECMA-262) version:

  if (!Array.prototype.indexOf)
  {

       Array.prototype.indexOf = function(searchElement /*, fromIndex */)

    {


    "use strict";

    if (this === void 0 || this === null)
      throw new TypeError();

    var t = Object(this);
    var len = t.length >>> 0;
    if (len === 0)
      return -1;

    var n = 0;
    if (arguments.length > 0)
    {
      n = Number(arguments[1]);
      if (n !== n)
        n = 0;
      else if (n !== 0 && n !== (1 / 0) && n !== -(1 / 0))
        n = (n > 0 || -1) * Math.floor(Math.abs(n));
    }

    if (n >= len)
      return -1;

    var k = n >= 0
          ? n
          : Math.max(len - Math.abs