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Re: Dynamically add/remove code in browsers

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Thomas Lahn wrote:

> You cannot assume that the script has been loaded and executed once you 
> inserted the “script” element in the document.
> 
> You need to listen to and handle the “load” event of the “script” element:
> 
>   sc.onload = function () {
>     el.onclick = handleClick;
>   };
> 
> But it is presently unknown to me where this feature now standardized in 
> HTML5 is supported.  Thus, it may be necessary to use setTimeout()-based 
> polling to determine if execution has reached the end of the loaded script 
> before you continue.

onload is not supported in IE8 and below. So, in this case, one could
use the readystatechange event. E.g.:

// IE8 and below
if (sc.readyState) {
  sc.onreadystatechange = function () {
    if (sc.readyState == "loaded" || sc.readyState == "complete") {
      script.onreadystatechange = null;
      el.onclick = handleClick;
    }
  };
} else { // FF, Chrome, Safari, Opera, etc.
  sc.onload = function () {
    el.onclick = handleClick;
  };
}

An alternate method would be XMLHttpRequest() which works in all modern
browsers. A caveat is the same-origin policy, which prevents downloading
the script from CDNs for instance.

> 
> Also, you can use the “document.head” property if it is available:
> 
>   (document.head || document.getElementsByTagName("head")[0])
>     .appendChild(sc);
> 
> It might be easier to use the backwards-compatible “document.body” property 
> instead:
> 
>   document.body.appendChild(sc);
> 

document.body.appendChild(sc) could be problematic in older versions of
IE. See
<http://www.nczonline.net/blog/2008/03/17/the-dreaded-operation-aborted-error/>

-- 
Joao Rodrigues

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Dynamically add/remove code in browsers "Leonardo Azpurua" <leonardo@exmvps.org> - 2015-01-12 05:22 -0430
  Re: Dynamically add/remove code in browsers Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-12 17:21 +0100
    Re: Dynamically add/remove code in browsers Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2015-01-12 16:44 -0200
      Re: Dynamically add/remove code in browsers Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-12 22:01 +0100
        Re: Dynamically add/remove code in browsers Joao Rodrigues <groups_jr-1@yahoo.com> - 2015-01-12 22:06 -0200
          Re: Dynamically add/remove code in browsers Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-13 01:11 +0100
    Re: Dynamically add/remove code in browsers "Leonardo Azpurua" <leonardo@exmvps.org> - 2015-01-12 15:21 -0430
      Re: Dynamically add/remove code in browsers Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-12 22:03 +0100
    Re: Dynamically add/remove code in browsers Joao Rodrigues <groups_jr-1@yahoo.com.br> - 2015-01-13 12:17 -0200
      Re: Dynamically add/remove code in browsers Thomas 'PointedEars' Lahn <PointedEars@web.de> - 2015-01-13 20:50 +0100

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