How do I check if an array includes an object in JavaScript

Questions

What is the most concise and efficient way to find out if a JavaScript array contains an object?

This is the only way I know to do it:

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

Is there a better and more concise way to accomplish this?

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

Answers

https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes#Polyfill https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/includes#Polyfill

http://api.jquery.com/jquery.inarray/ http://api.jquery.com/jquery.inarray/

http://underscorejs.org/#indexOf http://underscorejs.org/#indexOf

Some other frameworks offer similar methods:

http://dojotoolkit.org/reference-guide/dojo/indexOf.html http://dojotoolkit.org/reference-guide/dojo/indexOf.html http://api.prototypejs.org/language/Array/prototype/indexOf/ http://api.prototypejs.org/language/Array/prototype/indexOf/ http://mootools.net/docs/core/Native/Array#Array:indexOf http://mootools.net/docs/core/Native/Array#Array:indexOf http://mochi.github.io/mochikit/doc/html/MochiKit/Base.html#fn-findvalue http://mochi.github.io/mochikit/doc/html/MochiKit/Base.html#fn-findvalue http://www.asp.net/ajaxlibrary/Reference.Array-indexOf-Function.ashx http://www.asp.net/ajaxlibrary/Reference.Array-indexOf-Function.ashx http://docs.sencha.com/extjs/4.0.0/#/api/Ext.Array-method-contains http://docs.sencha.com/extjs/4.0.0/#/api/Ext.Array-method-contains https://lodash.com/docs#includes https://lodash.com/docs#includes

Notice that some frameworks implement this as a function, while others add the function to the array prototype.

Languages that compile to JavaScript

http://coffeescript.org/#try:a%20%3D%20[1%2C%202%2C%203%2C%204]%0Aalert%282%20in%20a%29 http://coffeescript.org/#try:a%20%3D%20[1%2C%202%2C%203%2C%204]%0Aalert%282%20in%20a%29

a = [1, 2, 3, 4]
alert(2 in a)

http://www.dartlang.org/docs/dart-up-and-running/ch03.html#ch03-collections http://www.dartlang.org/docs/dart-up-and-running/ch03.html#ch03-collections

var mylist = [1, 2, 3];
assert(mylist.contains(1));
assert(mylist.indexOf(1) == 0);

Source

License : cc by-sa 3.0

http://stackoverflow.com/questions/237104/how-do-i-check-if-an-array-includes-an-object-in-javascript

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