Detect when page loaded with firefox extension

firefox, firefox-addon

Solution

https://developer.mozilla.org/en/Code_snippets/On_page_load

Dont miss this part: "

Current Firefox trunk nightlies will fire the onPageLoad function for not only documents, but xul:images (favicons in tabbrowser). If you only want to handle documents, ensure aEvent.originalTarget.nodeName == "#document" 1.

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Problem

How to detect when a page is loaded (in any tab) with a firefox extension (automatically, no start-button or anything) (and display an alert message for example) ?

Original source