(function() {
    function _$(els) {
        this.elements = []; 
        this.elements = Array.prototype.slice.call(document.querySelectorAll(els));
        return this;
    }
    _$.prototype ={
    size: function() {
      alert('size:'+this.elements.length);
      return this;
    }
    };
    window.$ = function(args) { return new _$(args); }
})();

document.querySelectorAll('[object Arguments]')