Here you can find the source of minus(a)
Array.prototype.minus = function(a) { return this.filter(function(i) { return a.indexOf(i) < 0; }); };
Array.minus = function(a, b){ return a.uniquelize().each(function(o){return b.contains(o) ? null : o}); };
Array.prototype.minus = function (arr) { var result = new Array(); var obj = {}; for (var i = 0; i < arr.length; i++) { obj[arr[i]] = 1; for (var j = 0; j < this.length; j++) { if (!obj[this[j]]) obj[this[j]] = 1; result.push(this[j]); return result; };
Array.prototype.minus = function(b) { var array = new Array(); var ua = this.uniquelize(); var length = this.length; for (var i = 0; i < length; i++) { if (!b.inArray(ua[i])) { array.push(ua[i]); return array; };
Array.prototype.minus = function (list) { var result = []; for (var i = 0; i < this.length; i++) { if (list.indexOf(this[i]) < 0) result.push(this[i]); return result; };