Getting notified when the page DOM has loaded (but

2020-02-04 06:17发布

站内问答 / JavaScript
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I know there are some ways to get notified when the page body has loaded (before all the images and 3rd party resources load which fires the window.onload event), but it's different for every browser.

Is there a definitive way to do this on all the browsers?

So far I know of:

  • DOMContentLoaded : On Mozilla, Opera 9 and newest WebKits. This involves adding a listener to the event:

    document.addEventListener( "DOMContentLoaded", [init function], false );

  • Deferred script: On IE, you can emit a SCRIPT tag with a @defer attribute, which will reliably only load after the closing of the BODY tag.

  • Polling: On other browsers, you can keep polling, but is there even a standard thing to poll for, or do you need to do different things on each browser?

I'd like to be able to go without using document.write or external files.

This can be done simply via jQuery:

$(document).ready(function() { ... })

but, I'm writing a JS library and can't count on jQuery always being there.

9条回答
三岁会撩人
2楼-- · 2020-02-04 06:37

Using a library like jQuery will save you countless hours of browsers inconsistencies.

In this case with jQuery you can just

$(document).ready ( function () {
    //your code here
});

If you are curious you can take a look at the source to see how it is done, but is this day and age I don't think anyone should be reinventing this wheel when the library writer have done all the painful work for you.

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贼婆χ
3楼-- · 2020-02-04 06:41

There's no cross-browser method for checking when the DOM is ready -- this is why libraries like jQuery exist, to abstract away nasty little bits of incompatibility.

Mozilla, Opera, and modern WebKit support the DOMContentLoaded event. IE and Safari need weird hacks like scrolling the window or checking stylesheets. The gory details are contained in jQuery's bindReady() function.

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聊天终结者
4楼-- · 2020-02-04 06:46

YUI uses three tests to do this: for Firefox and recent WebKit there's a DOMContentLoaded event that is fired. For older Safari the document.readyState watched until it becomes "loaded" or "complete". For IE an HTML <P> tag is created and the "doScroll()" method called which should error out if the DOM is not ready. The source for YAHOO.util.Event shows YUI-specific code. Search for "doScroll" in the Event.js.

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叼着烟拽天下
5楼-- · 2020-02-04 06:48

I found this page, which shows a compact self-contained solution. It seems to work on every browser and has an explanation on how:

http://www.kryogenix.org/days/2007/09/26/shortloaded

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Root（大扎）
6楼-- · 2020-02-04 06:48

Just take the relevant piece of code from jQuery, John Resig has covered most of the bases on this issue already in jQuery.

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别忘想泡老子
7楼-- · 2020-02-04 06:56

Why not this: 

<body>  
  <!-- various content -->  
  <script type="text/javascript">  
  <!--  
    myInit();  
  -->
  </script>  
</body>

If I understand things correctly, myInit is gonna get executed as soon as browser hit it in the page, which is last thing in a body.

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