difference/index.js

Calculate the difference of two arrays

var Difference = module.exports = function difference(a, b) {
    if (b.length > a.length) {
        var tmp = a;
        a = b;
        b = tmp;
    }

    var o_a = {};
    var o_b = {};

    for (var i = 0; i < a.length; i += 1) {
        o_a[a[i]] = a[i];
    }

    for (var i = 0; i < b.length; i += 1) {
        o_b[b[i]] = b[i];
    }


    var result = [];
    for (var key in o_b) {
        if (o_a[key] === undefined) result.push(o_b[key]);
    }
    for (var key in o_a) {
        if (o_b[key] === undefined) result.push(o_a[key]);
    }
    return result;
}