text: function $(id){
  	return document.getElementById(id);
  }
  /*创建异步对象xhr*/
  function createXhr(){
  	var xhr=null;
  	if(window.XMLHttpRequest){
  		 xhr=new XMLHttpRequest();
  		
  	}else{
  		 xhr=new ActiveXObject("Microsoft.XMLHttp");
  	}
  	return xhr;
  }