Javascript - check two arrays for same value

Question

I have three arrays. One with static values, the other one has dynamic values, one array which will be filled with values that are the equal in the two arrays.

I would like to loop through the arrays and search for equal values. When a equal value has been found, this value should be put inside another array.

Something like this:

Array1 = ["Store1", "Store2", "Store3", "Store4"];
Array2 = ["Store6", "Store1", "Store3", "Store999"];
MatchedArray = ["Store1", "Store3"]; // should be filled with this

However, I don't like the idea of two for loops, like this:

 for(var arr1 = 0; arr1 < Array1.length; i++){
 for(var arr2 = 0; arr2 < Array2.length; i++){
 if(Array1[arr1].toLowerCase() == Array2[arr2].toLowerCase(){
 console.log('store found');
 duplicateArray.push(Array1[i].toLowerCase());
 }
 }
 }

I would like to know how I can use the .map or filter function or some other ways to accomplish this.

• user3297291: Possible duplicate of Simplest code for array intersection in javascript
• Elvira: You're right. Think this one can be closed due to duplication.

Answer 1

You can use a combination of Array#filter and Array#includes :

const arr1 = [ 'Store1', 'Store2', 'Store3', 'Store4'];
let arr2 = [ 'Store6', 'Store1', 'Store3', 'Store999'];
let res = arr2.filter(e => arr1.includes(e));
console.log(res);

Answer 2

Or make a generic array intersection function

 var intersection = function(){
 return Array.from(arguments).reduce(function(previous, current){
 return previous.filter(function(element){
 return current.indexOf(element) > -1;
 });
 });
 };
 var x = intersection([1,2,3],[2,3,4]); // or pass n number of array as an argument
 console.log(x);

Answer 3

Filter one of the arrays, and check if the other one contains the item using Array.includes():

var Array1 = [ 'Store1', 'Store2', 'Store3', 'Store4'];
var Array2 = [ 'Store6', 'Store1', 'Store3', 'Store999'];
var MatchedArray = Array1.filter(function(s) {
 return Array2.includes(s);
});
console.log(MatchedArray);

• Elvira: There are so many answers.. But I've chosen this one to test it out. :)

Answer 4

var Array1 = [ "Store1", "Store2", "Store3", "Store4"];
var Array2 = [ "Store6", "Store1", "Store3", "Store999"];
var Array3 = Array1 .filter(function(val) {
return Array2 .indexOf(val) != -1;
});
Array3
(2) ["Store1", "Store3"]

Answer 5

You can use array.filter method to get the desired result,

var filtered = arr1.filter(function(val) {
 return arr2.indexOf(val) >= 0
})

This function is filtering array items based on the given condition. The condition here is I'm checking whether the val is present in arr2 or not.

Answer 6

If you consider Underscore.js here is the way for such kind of operation, for any number of array

var Array1 = [ 'Store1', 'Store2', 'Store3', 'Store4'];
var Array2 = [ 'Store6', 'Store1', 'Store3', 'Store999'];
var Array3 = [ 'Store1', 'Store5', 'Store3', 'Store201'];
var common = _.intersection( Array1 ,Array2, Array3);
console.log(common);

<script src="https://cdnjs.cloudflare.com/ajax/libs/underscore.js/1.8.3/underscore-min.js"></script>