How to find the array index with a value?
JavascriptArraysIndexofJavascript Problem Overview
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.
Javascript Solutions
Solution 1 - Javascript
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 - Javascript
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 - Javascript
Use jQuery's function jQuery.inArray
jQuery.inArray( value, array [, fromIndex ] )
(or) $.inArray( value, array [, fromIndex ] )
Solution 4 - Javascript
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 - Javascript
Use indexOf
imageList.indexOf(200)
Solution 6 - Javascript
how about indexOf
?
alert(imageList.indexOf(200));
Solution 7 - Javascript
Array.indexOf
doesnt work in some versions of internet explorer - there are lots of alternative ways of doing it though ... see this question / answer : https://stackoverflow.com/questions/237104/array-containsobj-in-javascript
Solution 8 - Javascript
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);
Solution 9 - Javascript
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');
Solution 10 - Javascript
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);
}
}
Solution 11 - Javascript
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);
}
Solution 12 - Javascript
// 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)