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@fearphage
Forked from edvakf/defer_async_script.js
Created March 22, 2011 14:18
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async/defer support for Opera
// ==UserScript==
// @name defer/async for Opera
// @namespace http://d.hatena.ne.jp/edvakf/
// @license Public Domain
// ==/UserScript==
(function(window, document, opera) {
function load_script(script, attr) {
return function() {
var script2 = script.cloneNode(true);
script2.removeAttribute(attr);
script.parentNode.insertBefore(script2, script);
script.parentNode.removeChild(script);
};
}
var asyncSupport = 'async' in document.createElement('script');
// support async and defer
opera.addEventListener('BeforeExternalScript', function(e) {
var script = e.element;
if (!asyncSupport && script.hasAttribute('async')) {
setTimeout(load_script(script, 'async'), 10);
return e.preventDefault();
}
if (script.hasAttribute('defer') && document.readyState != 'complete') {
window.addEventListener('load', load_script(script, 'defer'), false);
return e.preventDefault();
}
}, false);
})(this, this.document, this.opera);
@edvakf
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edvakf commented Jun 14, 2011

Are your suggesting us to make it into an extension, Paul?

This script works fine by itself, but if someone installed another script that listens to BeforeExternalScript event (Opera's privileged event) and do something as hacky as this one, then it may possibly fail.

According to the test cases, it does have measurable impact. However, I haven't bothered checking in real sites. Are there example of sites that use async/defer?

@webkeke
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webkeke commented Aug 22, 2016

Hello, this code need to penetrate the parameters? Or can be directly used?

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