How to determine if Javascript array contains an object with an attribute that equals a given value?
JavascriptArraysJavascript Problem Overview
I have an array like
vendors = [{
Name: 'Magenic',
ID: 'ABC'
},
{
Name: 'Microsoft',
ID: 'DEF'
} // and so on...
];
How do I check this array to see if "Magenic" exists? I don't want to loop, unless I have to. I'm working with potentially a couple thousand records.
Javascript Solutions
Solution 1 - Javascript
No need to reinvent the wheel loop, at least not explicitly (using arrow functions, modern browsers only):
if (vendors.filter(e => e.Name === 'Magenic').length > 0) {
/* vendors contains the element we're looking for */
}
or, better yet, as it allows the browser to stop as soon as one element is found that matches, so it's going to be faster:
if (vendors.some(e => e.Name === 'Magenic')) {
/* vendors contains the element we're looking for */
}
EDIT: If you need compatibility with lousy browsers then your best bet is:
if (vendors.filter(function(e) { return e.Name === 'Magenic'; }).length > 0) {
/* vendors contains the element we're looking for */
}
Solution 2 - Javascript
2018 edit: This answer is from 2011, before browsers had widely supported array filtering methods and arrow functions. Have a look at CAFxX's answer.
There is no "magic" way to check for something in an array without a loop. Even if you use some function, the function itself will use a loop. What you can do is break out of the loop as soon as you find what you're looking for to minimize computational time.
var found = false;
for(var i = 0; i < vendors.length; i++) {
if (vendors[i].Name == 'Magenic') {
found = true;
break;
}
}
Solution 3 - Javascript
No loop necessary. Three methods that come to mind:
Array.prototype.some()
This is the most exact answer for your question, i.e. "check if something exists", implying a bool result. This will be true if there are any 'Magenic' objects, false otherwise:
let hasMagenicVendor = vendors.some( vendor => vendor['Name'] === 'Magenic' )
Array.prototype.filter()
This will return an array of all 'Magenic' objects, even if there is only one (will return a one-element array):
let magenicVendors = vendors.filter( vendor => vendor['Name'] === 'Magenic' )
If you try to coerce this to a boolean, it will not work, as an empty array (no 'Magenic' objects) is still truthy. So just use magenicVendors.length
in your conditional.
Array.prototype.find()
This will return the first 'Magenic' object (or undefined
if there aren't any):
let magenicVendor = vendors.find( vendor => vendor['Name'] === 'Magenic' );
This coerces to a boolean okay (any object is truthy, undefined
is falsy).
Note: I'm using vendor["Name"] instead of vendor.Name because of the weird casing of the property names.
Note 2: No reason to use loose equality (==) instead of strict equality (===) when checking the name.
Solution 4 - Javascript
The accepted answer still works but now we have an ECMAScript 6 native methods [Array.find][1]
and [Array.some][2]
to achieve the same effect.
Array.some
Use some
If you only want to determine if an element exists i.e. you need a true/false
determination.
Quoting MDN:
>The some() method tests whether at least one element in the array passes the test implemented by the provided function. It returns true if, in the array, it finds an element for which the provided function returns true; otherwise it returns false. It doesn't modify the array.
Array.find
Use find if you want to get the matched object from array else returns undefined
.
Quoting MDN:
> The find() method returns the value of the first element in the provided array that satisfies the provided testing function. If no values satisfy the testing function, undefined is returned.
var arr = [];
var item1 = {
id: 21,
label: 'Banana',
};
var item2 = {
id: 22,
label: 'Apple',
};
arr.push(item1, item2);
/* note : data is the actual object that matched search criteria
or undefined if nothing matched */
var data = arr.find(function(ele) {
return ele.id === 21;
});
if (data) {
console.log('found');
console.log(data); // This is entire object i.e. `item` not boolean
}
/* note : doesExist is a boolean thats true or false depending on of whether the data was found or not */
var doesExist = arr.some(function(ele) {
return ele.id === 21;
});
See my jsfiddle link There is a polyfill for IE provided by mozilla
Solution 5 - Javascript
Here's the way I'd do it
const found = vendors.some(item => item.Name === 'Magenic');
array.some()
method checks if there is at least one value in an array that matches criteria and returns a boolean.
From here on you can go with:
if (found) {
// do something
} else {
// do something else
}
Solution 6 - Javascript
Unless you want to restructure it like this:
vendors = {
Magenic: {
Name: 'Magenic',
ID: 'ABC'
},
Microsoft: {
Name: 'Microsoft',
ID: 'DEF'
} and so on...
};
to which you can do if(vendors.Magnetic)
You will have to loop
Solution 7 - Javascript
As per ECMAScript 6 specification, you can use findIndex
.
const magenicIndex = vendors.findIndex(vendor => vendor.Name === 'Magenic');
magenicIndex
will hold either 0
(which is the index in the array) or -1
if it wasn't found.
Solution 8 - Javascript
As the OP has asked the question if the key exists or not.
A more elegant solution that will return boolean using ES6 reduce function can be
const magenicVendorExists = vendors.reduce((accumulator, vendor) => (accumulator||vendor.Name === "Magenic"), false);
Note: The initial parameter of reduce is a false
and if the array has the key it will return true.
Hope it helps for better and cleaner code implementation
Solution 9 - Javascript
May be too late, but javascript array has two methods some
and every
method that returns a boolean and can help you achieve this.
I think some
would be most appropriate for what you intend to achieve.
vendors.some( vendor => vendor['Name'] !== 'Magenic' )
Some validates that any of the objects in the array satisfies the given condition.
vendors.every( vendor => vendor['Name'] !== 'Magenic' )
Every validates that all the objects in the array satisfies the given condition.
Solution 10 - Javascript
You cannot without looking into the object really.
You probably should change your structure a little, like
vendors = {
Magenic: 'ABC',
Microsoft: 'DEF'
};
Then you can just use it like a lookup-hash.
vendors['Microsoft']; // 'DEF'
vendors['Apple']; // undefined
Solution 11 - Javascript
Testing for array elements:
JS Offers array functions which allow you to achieve this relatively easily. They are the following:
Array.prototype.filter
: Takes a callback function which is a test, the array is then iterated over with is callback and filtered according to this callback. A new filtered array is returned.Array.prototype.some
: Takes a callback function which is a test, the array is then iterated over with is callback and if any element passes the test, the boolean true is returned. Otherwise false is returned
The specifics are best explained via an example:
Example:
vendors = [
{
Name: 'Magenic',
ID: 'ABC'
},
{
Name: 'Microsoft',
ID: 'DEF'
} //and so on goes array...
];
// filter returns a new array, we instantly check if the length
// is longer than zero of this newly created array
if (vendors.filter(company => company.Name === 'Magenic').length ) {
console.log('I contain Magenic');
}
// some would be a better option then filter since it directly returns a boolean
if (vendors.some(company => company.Name === 'Magenic')) {
console.log('I also contain Magenic');
}
Browser support:
These 2 function are ES6
function, not all browsers might support them. To overcome this you can use a polyfill. Here is the polyfill for Array.prototype.some
(from MDN):
if (!Array.prototype.some) {
Array.prototype.some = function(fun, thisArg) {
'use strict';
if (this == null) {
throw new TypeError('Array.prototype.some called on null or undefined');
}
if (typeof fun !== 'function') {
throw new TypeError();
}
var t = Object(this);
var len = t.length >>> 0;
for (var i = 0; i < len; i++) {
if (i in t && fun.call(thisArg, t[i], i, t)) {
return true;
}
}
return false;
};
}
Solution 12 - Javascript
const check = vendors.find((item)=>item.Name==='Magenic')
console.log(check)
Try this code.
If the item or element is present then the output will show you that element. If it is not present then the output will be 'undefined'.
Solution 13 - Javascript
2021 Solution*
Lodash .some
(docs) is a clean solution, if you use the _matchesProperty
(docs) shorthand:
_.some(VENDORS, ['Name', 'Magenic'])
Explanation
This will iterate through the VENDORS
Array looking for an element Object with the Name
key having a value of the String 'Magenic'
. Once it finds this element, it returns true
and stops iterating. If it doesn't find the element after looking through the entire Array, it returns false
.
Code snippet
const VENDORS = [{ Name: 'Magenic', ID: 'ABC' }, { Name: 'Microsoft', ID: 'DEF' }];
console.log(_.some(VENDORS, ['Name', 'Magenic'])); // true
<script src="https://cdn.jsdelivr.net/npm/[email protected]/lodash.min.js"></script>
*
Note that this uses the popular lodash
library to achieve the simplest/shortest possible solution. I'm offering this as an alternative to the existing vanilla JS solutions, for those who are interested.
Solution 14 - Javascript
Functions map
, filter
, find
, and similar are slower than the simple loop.
For me they also less readable than the simple loop and harder to debug. Using them looks like a kind of irrational ritual.
Better have something like this:
arrayHelper = {
arrayContainsObject: function (array, object, key){
for (let i = 0; i < array.length; i++){
if (object[key] === array[i][key]){
return true;
}
}
return false;
}
};
And use it like this with given OP example:
vendors = [{
Name: 'Magenic',
ID: 'ABC'
},
{
Name: 'Microsoft',
ID: 'DEF'
}
];
let abcObject = {ID: 'ABC', Name: 'Magenic'};
let isContainObject = arrayHelper.arrayContainsObject(vendors, abcObject, 'ID');
Solution 15 - Javascript
You have to loop, there is no way around it.
function seekVendor(vendors, name) {
for (var i=0, l=vendors.length; i<l; i++) {
if (typeof vendors[i] == "object" && vendors[i].Name === name) {
return vendors[i];
}
}
}
Of course you could use a library like linq.js to make this more pleasing:
Enumerable.From(vendors).Where("$.Name == 'Magenic'").First();
(see jsFiddle for a demo)
I doubt that linq.js will be faster than a straight-forward loop, but it certainly is more flexible when things get a little more complicated.
Solution 16 - Javascript
Correct me if i'm wrong..
i could have used forEach
method like this,
var found=false;
vendors.forEach(function(item){
if(item.name === "name"){
found=true;
}
});
Nowadays i'm used to it ,because of it simplicity and self explanatory word. Thank you.
Solution 17 - Javascript
My approach to solving this problem is to use ES6 and creating a function that does the check for us. The benefit of this function is that it can be reusable through out your project to check any array of objects given the key
and the value
to check.
ENOUGH TALK, LET'S SEE THE CODE
Array
const ceos = [
{
name: "Jeff Bezos",
company: "Amazon"
},
{
name: "Mark Zuckerberg",
company: "Facebook"
},
{
name: "Tim Cook",
company: "Apple"
}
];
Function
const arrayIncludesInObj = (arr, key, valueToCheck) => {
return arr.some(value => value[key] === valueToCheck);
}
Call/Usage
const found = arrayIncludesInObj(ceos, "name", "Tim Cook"); // true
const found = arrayIncludesInObj(ceos, "name", "Tim Bezos"); // false
Solution 18 - Javascript
if you're using jquery you can take advantage of grep to create array with all matching objects:
var results = $.grep(vendors, function (e) {
return e.Name == "Magenic";
});
and then use the results array:
for (var i=0, l=results.length; i<l; i++) {
console.log(results[i].ID);
}
Solution 19 - Javascript
You can use lodash. If lodash library is too heavy for your application consider chunking out unnecessary function not used.
let newArray = filter(_this.props.ArrayOne, function(item) {
return find(_this.props.ArrayTwo, {"speciesId": item.speciesId});
});
This is just one way to do this. Another one can be:
var newArray= [];
_.filter(ArrayOne, function(item) {
return AllSpecies.forEach(function(cItem){
if (cItem.speciesId == item.speciesId){
newArray.push(item);
}
})
});
console.log(arr);
The above example can also be rewritten without using any libraries like:
var newArray= [];
ArrayOne.filter(function(item) {
return ArrayTwo.forEach(function(cItem){
if (cItem.speciesId == item.speciesId){
newArray.push(item);
}
})
});
console.log(arr);
Hope my answer helps.
Solution 20 - Javascript
Many answers here are good and pretty easy. But if your array of object is having a fixed set of value then you can use below trick:
Map all the name in a object.
vendors = [
{
Name: 'Magenic',
ID: 'ABC'
},
{
Name: 'Microsoft',
ID: 'DEF'
}
];
var dirtyObj = {}
for(var count=0;count<vendors.length;count++){
dirtyObj[vendors[count].Name] = true //or assign which gives you true.
}
Now this dirtyObj you can use again and again without any loop.
if(dirtyObj[vendor.Name]){
console.log("Hey! I am available.");
}
Solution 21 - Javascript
To compare one object to another, I combine a for in loop (used to loop through objects) and some(). You do not have to worry about an array going out of bounds etc, so that saves some code. Documentation on .some can be found here
var productList = [{id: 'text3'}, {id: 'text2'}, {id: 'text4', product: 'Shampoo'}]; // Example of selected products
var theDatabaseList = [{id: 'text1'}, {id: 'text2'},{id: 'text3'},{id:'text4', product: 'shampoo'}];
var objectsFound = [];
for(let objectNumber in productList){
var currentId = productList[objectNumber].id;
if (theDatabaseList.some(obj => obj.id === currentId)) {
// Do what you need to do with the matching value here
objectsFound.push(currentId);
}
}
console.log(objectsFound);
An alternative way I compare one object to another is to use a nested for loop with Object.keys().length to get the amount of objects in the array. Code below:
var productList = [{id: 'text3'}, {id: 'text2'}, {id: 'text4', product: 'Shampoo'}]; // Example of selected products
var theDatabaseList = [{id: 'text1'}, {id: 'text2'},{id: 'text3'},{id:'text4', product: 'shampoo'}];
var objectsFound = [];
for(var i = 0; i < Object.keys(productList).length; i++){
for(var j = 0; j < Object.keys(theDatabaseList).length; j++){
if(productList[i].id === theDatabaseList[j].id){
objectsFound.push(productList[i].id);
}
}
}
console.log(objectsFound);
To answer your exact question, if are just searching for a value in an object, you can use a single for in loop.
var vendors = [
{
Name: 'Magenic',
ID: 'ABC'
},
{
Name: 'Microsoft',
ID: 'DEF'
}
];
for(var ojectNumbers in vendors){
if(vendors[ojectNumbers].Name === 'Magenic'){
console.log('object contains Magenic');
}
}
Solution 22 - Javascript
Alternatively you can do:
const find = (key, needle) => return !!~vendors.findIndex(v => (v[key] === needle));
Solution 23 - Javascript
Example:
Result: without2([{id:1},{id:1},{id:2}],{id:2})
Solution 24 - Javascript
You can try this its work for me.
const _ = require('lodash');
var arr = [
{
name: 'Jack',
id: 1
},
{
name: 'Gabriel',
id: 2
},
{
name: 'John',
id: 3
}
]
function findValue(arr,value) {
return _.filter(arr, function (object) {
return object['name'].toLowerCase().indexOf(value.toLowerCase()) >= 0;
});
}
console.log(findValue(arr,'jack'))
//[ { name: 'Jack', id: 1 } ]
Solution 25 - Javascript
const a = [{one:2},{two:2},{two:4}]
const b = a.filter(val => "two" in val).length;
if (b) {
...
}
Solution 26 - Javascript
Simplest method so far
if(vendors.findIndex(item => item.Name == "Magenic") == -1){
//not found item
}else{
//found item
}
Solution 27 - Javascript
I would rather go with regex.
If your code is as follows,
vendors = [
{
Name: 'Magenic',
ID: 'ABC'
},
{
Name: 'Microsoft',
ID: 'DEF'
}
];
I would recommend
/"Name":"Magenic"/.test(JSON.stringify(vendors))