underscore.js - Is there a function that produces an array thats the difference of two arrays?

Question

Looking for a function in underscore.js that will take 2 arrays and return a new array of unique values? Something like _without

_.without([0, 1, 3, 9], [1, 3])         


        

Answer 1

_.without.apply(_, [arr1].concat(arr2))

[[0, 1, 3, 9]].concat([1, 3]) is [[0, 1, 3, 9], 1, 3];

_.without.apply(_, [[0, 1, 3, 9], 1, 3]) is _.without([0, 1, 3, 9], 1, 3)

You've got a perfectly good _.without method. So just convert an array into a list of values you can pass into a function. This is the purpose of Function.prototype.apply

Answer 2

var result = _.reject([0, 1, 3, 9], function(num) {
                return _.include([1, 3], num);
            });

Answer 3

The _.difference function should give you what you're looking for:

_.difference([0, 1, 3, 9], [1, 3]); // => [0, 9]

Answer 4

Lo-Dash is extended Underscore and here is what you need: http://lodash.com/docs#xor

_.xor

Creates an array that is the symmetric difference of the provided arrays. See http://en.wikipedia.org/wiki/Symmetric_difference.

_.xor([1, 2, 3], [5, 2, 1, 4]);
// → [3, 5, 4]