Reputation: 18353

How to find the array index with a value?

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.

Upvotes: 246

Answers (12)

Souleste

Reputation: 1984

In a multidimensional array.

Reference array:

var array = [
    { ID: '100' },
    { ID: '200' },
    { ID: '300' },
    { ID: '400' },
    { ID: '500' }
];

Using filter and indexOf:

var index = array.indexOf(array.filter(function(item) { return item.ID == '200' })[0]);

Looping through each item in the array using indexOf:

for (var i = 0; i < array.length; i++) {
    var item = array[i];
    if (item.ID == '200') { 
        var index = array.indexOf(item);
    }
}

Upvotes: 4

voigtan

Reputation: 9031

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.

Upvotes: 374

Jaqen H'ghar

Reputation: 16804

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

Upvotes: 106

ricks

Reputation: 3324

Here is my take on it, seems like most peoples solutions don't check if the item exists and it removes random values if it does not exist.

First check if the element exists by looking for it's index. If it does exist, remove it by its index using the splice method

elementPosition = array.indexOf(value);

if(elementPosition != -1) {
  array.splice(elementPosition, 1);
}

Upvotes: 0

Harshi Srivastava

Reputation: 151

// Instead Of 
var index = arr.indexOf(200)

// Use 
var index = arr.includes(200);

Please Note: Includes function is a simple instance method on the array and helps to easily find if an item is in the array(including NaN unlike indexOf)

Upvotes: -1

StepUp

Reputation: 38114

It is possible to use a ES6 function Array.prototype.findIndex.

MDN says:

The findIndex() method returns the index of the first element in the array that satisfies the provided testing function. Otherwise -1 is returned.

var fooArray = [5, 10, 15, 20, 25];
console.log(fooArray.findIndex(num=> { return num > 5; }));

// expected output: 1

Find an index by object property.

To find an index by object property:

yourArray.findIndex(obj => obj['propertyName'] === yourValue)

For example, there is a such array:

let someArray = [
    { property: 'OutDate' },
    { property: 'BeginDate'},
    { property: 'CarNumber' },
    { property: 'FirstName'}
];

Then, code to find an index of necessary property looks like that:

let carIndex = someArray.findIndex( filterCarObj=> 
    filterCarObj['property'] === 'CarNumber');

Upvotes: 6

Ravinder Singh Bhanwar

Reputation: 824

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);

Upvotes: 17

Ryan

Reputation: 96

When the lists aren't extremely long, this is the best way I know:

function getIndex(val) {
    for (var i = 0; i < imageList.length; i++) {
        if (imageList[i] === val) {
            return i;
        }
    }
}

var imageList = [100, 200, 300, 400, 500];
var index = getIndex(200);

Upvotes: 6

Simon_Weaver

Reputation: 145950

Use jQuery's function jQuery.inArray

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

Upvotes: 18

Manse

Reputation: 38147

Array.indexOf doesnt work in some versions of internet explorer - there are lots of alternative ways of doing it though ... see this question / answer : How do I check if an array includes an object in JavaScript?

Upvotes: 7