behavior of iframe contentDocument in chrome and firefox

Question

Here is my testing.html:

<html>
<meta charset="utf-8">
<script>
window.onload = function() {
    var a = document.getElementById("divid");
    var ifr = document.createElement('iframe');
    a.appendChild(ifr);
    ifr.contentDocument.body.style.cssText = (
      'margin: 0px;' +
      'padding: 0px;' +
      'height: 100%;' +
      'width: 100%;');
}
</script>

<head></head>
<body>
<div id="divid"/>
</body>
</html>

Here ifr.contentDocument.body.style.cssText = (...) works fine on chrome but not on Firefox. Is it a firefox bug? Is there any workaround?

Found workaround: Looks like there is a weird race bug in firefox. The following workaround with setTimeout will make this work fine as shown below:

<html>
<meta charset="utf-8">
<script>
window.onload = function() {
    var a = document.getElementById("divid");
    var ifr = document.createElement('iframe');
    ifr.id = "fid";
    a.appendChild(ifr);
    setTimeout (function() {
        ifr.contentDocument.body.style.cssText = (
        'margin: 0px;' +
        'padding: 0px;' +
        'height: 100%;' +
        'width: 100%;');
    }, 100);
}
</script>

<head></head>
<body>
<div id="divid"/>
</body>
</html>

Here is exactly what you need: http://stackoverflow.com/questions/926916/how-to-get-the-bodys-content-of-an-iframe-in-javascript — Ivan Chernykh, May 05 '13 at 06:01

score 6 · Accepted Answer · answered May 05 '13 at 11:59

6

When you append the iframe in Firefox it starts loading about:blank in the iframe, asynchronously. Then you touch the document, so it has to synchronously create an about:blank document in there, and you modify it. Then the async load completes and replaces the document you modified.

Waiting for the load event on the frame to fire before modifying it would work.

answered May 05 '13 at 11:59

Boris Zbarsky

34,758
5
52
55

Thanks for the splain. Is there any way to get firefox not to do this? can I set the iframe's src attribute to a data uri or something? – JasonWoof Feb 02 '16 at 04:27
The it will be asynchronously loading the data URI. The right thing to do here is to wait for the load event. – Boris Zbarsky Feb 02 '16 at 19:06
@BorisZbarsky How to wait for the load event? – Jarod Mar 22 '21 at 13:23
In the case of the code above: `ifr.addEventListener("load", function() { /* do things */ });` – Boris Zbarsky Mar 23 '21 at 00:17

score 1 · Answer 2 · answered May 05 '13 at 05:34

1

try this:

 ifr.contentDocument.getElementsByTagName('body')[0].style.cssText = (
  'margin: 0px;' +
  'padding: 0px;' +
  'height: 100%;' +
  'width: 100%;');

also

<div id="divid"> </div>

answered May 05 '13 at 05:34

Prakash GPz

1,675
4
16
27

kaioker2 · Answer 3 · 2023-01-26T22:01:30.560

To expand on Boris' answer, Here be Dragons!

Although this will get Firefox working, it will currently also break Chrome, Opera, Safari, and all their mobile counterparts, as they will NOT throw the 'onLoad' event as on these platforms, the iframe sits idle until used.

You will need to make this a Firefox only exception. Luckily due to Firefox's frustrating lack of features, its pretty easy to tell them apart. Just look for something the rest of the internet has but Firefox does not, or vice versa.

if(typeof InstallTrigger !== 'undefined'){  //if ie, wait sorry, firefox
    iframe.onload = function(){
        iframe.contentDocument.body.appendChild(contents);
    }
}else{
    iframe.contentDocument.body.appendChild(contents);
}

Firefox, The new Internet Explorer

behavior of iframe contentDocument in chrome and firefox

3 Answers3