Array diff

1_array_diff_js.js

function getArrayDiff(a, b) {
    var ret = [];
    if (!(Array.isArray(a) && Array.isArray(b))) {
        return ret;
    }
    var i;
    var key;

    for (i = a.length - 1; i >= 0; i--) {
      key = a[i];
      if (-1 === b.indexOf(key)) {
        ret.push(key);
      }
    }

    return ret;
}

2_array_diff_lodash.js

_.difference(arr1, arr2);

// OR

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