链式操作

	var Base = function(id){
		this[0] = document.getElementById(id);
		return this;	 
	}
	var Class = function(id){
	  return new Base(id);
	}
	 
	Base.prototype = Class.prototype = {
		html: function(str){
			this[0].innerHTML = str;
			return this;
		},
		addClass: function(str){
			this[0].className += ' '+str;
			return this;
		}
	}
	 
	 
	var obj = Class('test');
	obj.html('111').addClass('xxx');