text: //用于获取bid
  //console.log("inject-bid.js被注入了");
  function getClass(classname){
  	if (document.getElementsByClassName) {
          //使用现有方法
  		return document.getElementsByClassName(classname);
  	}else{
  		//定义一个数组放classname
  		var results = new Array();
  		//获取所有节点元素
  		var elem = document.getElementsByTagName("*");
  		for (var i = 0; i < elem.length; i++) {
  			if (elem[i].className.indexOf(classname) != -1) {
  				results[results.length] = elem[i];
  			}
  		}
  		return results;
  	}
  }
  
  var element = getClass("wr_bookCover_img");
  var list = element.item(0).src.split("/");
  var bookId = list[list.length - 2];
  chrome.runtime.sendMessage({type:"getBid", bid: bookId});