js如何判断 iframe 是否完全加载

<code class="language-javascript">var iframe = document.createElement("iframe"); 
iframe.src = "http://www.manongjc.com"; 

if (!/*@cc_on!@*/0) { //if not IE 
iframe.onload = function(){ 
alert("Local iframe is now loaded."); 
}; 
} else { 
iframe.onreadystatechange = function(){ 
if (iframe.readyState == "complete"){ 
alert("Local iframe is now loaded."); 
} 
}; 
} 
document.body.appendChild(iframe); </code>

<code class="language-javascript">var iframe = document.createElement("iframe"); 
iframe.src = "http://manongjc.com"; 
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); </code>