How to find the array index with a value?

Question

Say I've got this

imageList = [100,200,300,400,500];

Which gives me

[0]100 [1]200 etc.

Is there any way in JavaScript to return the index with the value?

I.e. I want the index for 200, I get returned 1.

Solution 1

You can use indexOf:

var imageList = [100,200,300,400,500];
var index = imageList.indexOf(200); // 1

You will get -1 if it cannot find a value in the array.

Solution 2

For objects array use map with indexOf:

var imageList = [
   {value: 100},
   {value: 200},
   {value: 300},
   {value: 400},
   {value: 500}
];

var index = imageList.map(function (img) { return img.value; }).indexOf(200);

console.log(index);

---

In modern browsers you can use findIndex:

var imageList = [
   {value: 100},
   {value: 200},
   {value: 300},
   {value: 400},
   {value: 500}
];

var index = imageList.findIndex(img => img.value === 200);

console.log(index);

Its part of ES6 and supported by Chrome, FF, Safari and Edge

Solution 3

Use jQuery's function jQuery.inArray

jQuery.inArray( value, array [, fromIndex ] )
(or) $.inArray( value, array [, fromIndex ] )

Solution 4

Here is an another way find value index in complex array in javascript. Hope help somebody indeed. Let us assume we have a JavaScript array as following,

var studentsArray =
     [
    {
    "rollnumber": 1,
    "name": "dj",
    "subject": "physics"
   },
   {
   "rollnumber": 2,
  "name": "tanmay",
  "subject": "biology"
   },
  {
   "rollnumber": 3,
   "name": "amit",
   "subject": "chemistry"
   },
  ];

Now if we have a requirement to select a particular object in the array. Let us assume that we want to find index of student with name Tanmay.

We can do that by iterating through the array and comparing value at the given key.

function functiontofindIndexByKeyValue(arraytosearch, key, valuetosearch) {

    for (var i = 0; i < arraytosearch.length; i++) {

    if (arraytosearch[i][key] == valuetosearch) {
    return i;
    }
    }
    return null;
    }

You can use the function to find index of a particular element as below,

var index = functiontofindIndexByKeyValue(studentsArray, "name", "tanmay");
alert(index);

Solution 5

Use indexOf

imageList.indexOf(200)

View more solutions

Comments

[Manse]

Excellent answer here -> stackoverflow.com/questions/237104/…

[Matt Ball]

developer.mozilla.org/en/JavaScript/Reference/Global_Objects‌​/…

[voigtan]

you can use developer.mozilla.org/en/JavaScript/Reference/Global_Objects‌​/… or any Javascript framework to fix that.

[joedborg]

Have just found it won't work in IE8. What's my alternative?

[joedborg]

@voigtan How do I add this to my JS?

[joedborg]

I've done it, thanks. IE will one day catch up with modern times!

[aruno]

according to this page developer.mozilla.org/en-US/docs/JavaScript/Reference/… you need Internet Explorer 9 for this feature (I almost wrongly assumed we were just talking IE 6 here)

[Manse]

@Simon_Weaver on that page you linked there is a polyfill for all browsers using JavaScript 1.6 and up

[pelms]

Also won't work in recent IE if in compatibility mode

[James Blackburn]

Was going to use the code marked as the correct answer but it seems that that code wont work in all versions of IE. This answer works in all versions of IE but I changed the code slightly: var arrayPosition = $.inArray( value, Array ); works perfectly

[James Blackburn]

var arrayPosition = $.inArray( value, Array ); will work in all versions of IE

[Andrew]

jQuery ≠ Javascript

[Bindrid]

Note that findIndex is not implemented in IE 11

[Jaqen H'ghar]

@Bindrid it is written in the answer see "Its part of ES6 and supported by Chrome, FF, Safari and (Unfortunately only) IE edge"

[moto]

In addition to this only telling you if it exists, instead of getting the index/item, be cognizant of the compatibility (i.e. no IE): caniuse.com/#search=includes

[Heretic Monkey]

includes returns a Boolean indicating if the array contains the value specified.