Here you can find the source of isEmpty()
Array.prototype.isEmpty = function() { return this.length < 1 };
Array.prototype.isEmpty = function () { return this.length === 0 }; Array.prototype.last = function () { if (this.length === 0) return null; return this[this.length - 1]; };
Array.prototype.isEmpty = function(){ return (this.length === 0 );
Array.prototype.isEmpty = function() { return (0 === this.length);
Array.prototype.isEmpty = function() { return this.length == 0; };
Array.prototype.isEmpty = function() { return this.length == 0;
Array.prototype.isEmpty = function () { return this.length === 0; };
Array.prototype.isEmpty = function() { return this.length == 0 ? true : false; };
Array.prototype.is_empty = function() { return is_empty(this); };