判断 iframe 是否加载完成的完美方法

var iframe = document.createElement("iframe");iframe.src = "http://www.google.com.hk";if (iframe.attachEvent){    iframe.attachEvent("onload", function(){        alert("Local iframe is now loaded.");    });} else {    iframe.onload = function(){        alert("Local iframe is now loaded.");    };}document.body.appendChild(iframe);