Is there a way to return the difference between two arrays in JavaScript?
For example:
var a1 = ['a', 'b'];
var a2 = ['a', 'b', 'c', 'd'];
// need ["c", "d"]
There is a better way using ES7:
Intersection
let intersection = arr1.filter(x => arr2.includes(x));
For [1,2,3] [2,3]
it will yield [2,3]
. On the other hand, for [1,2,3] [2,3,5]
will return the same thing.
Difference
let difference = arr1.filter(x => !arr2.includes(x));
For [1,2,3] [2,3]
it will yield [1]
. On the other hand, for [1,2,3] [2,3,5]
will return the same thing.
For a symmetric difference, you can do:
let difference = arr1
.filter(x => !arr2.includes(x))
.concat(arr2.filter(x => !arr1.includes(x)));
This way, you will get an array containing all the elements of arr1 that are not in arr2 and vice-versa
As @Joshaven Potter pointed out on his answer, you can add this to Array.prototype so it can be used like this:
Array.prototype.diff = function(arr2) { return this.filter(x => !arr2.includes(x)); }
[1, 2, 3].diff([2, 3])