Challenges encountered with the "load" event handler when creating a Firefox Extension

Question

Challenges encountered with the "load" event handler when creating a Firefox Extension

I am currently troubleshooting a user interaction issue with my Firefox extension. The tasks that my extension needs to complete include:

Checking certain structures on the currently viewed browser tab
Making backend server calls
Opening dialogs
Redirecting the user to a landing page

Initially, everything seemed to be working fine. I began the sequence with the following eventHandler:

window.gBrowser.selectedTab.addEventListener("load",function(){ Fabogore.Load();},true);

However, after opening the dialog, I attempted to remove the EventHandler from within the dialog like this:

window.opener.gBrowser.selectedTab.removeEventListener("load",function(){Fabogore.Load();},true);

Despite using selectedTab, the sequence kept getting triggered repeatedly as the event listener was fetching every load event from every single tab. This resulted in the dialog popping up multiple times. I also tried closing the event Handler in the original Javascript.

Any thoughts on what might be causing this issue?

javascript dialog event-handling firefox-addon dom-events

Answer 1

Answer №1

The issue here is quite simple - when you add a listener function and then try to remove it, they are not the same function. To demonstrate this, run the following code:

alert(function(){ Fabogore.Load();} == function(){ Fabogore.Load();});

You will see false as the result because each time you define a function in your code, a brand new function is created. The solution to your problem is to define one function, save the reference to it, and use that same function for both adding and removing the listener:

var listener = function(){ Fabogore.Load();};
var listenerTab = window.gBrowser.selectedTab;
listenerTab.addEventListener("load", listener, true);
[...]
listenerTab.removeEventListener("load", listener, true);

It's important to note that I also saved the value of window.gBrowser.selectedTab in a variable. This ensures that when you remove the listener, it is from the same tab where you added it initially, preventing any confusion if the selected tab changes.

Answer 2

The issue here is quite simple - when you add a listener function and then try to remove it, they are not the same function. To demonstrate this, run the following code:

alert(function(){ Fabogore.Load();} == function(){ Fabogore.Load();});

You will see false as the result because each time you define a function in your code, a brand new function is created. The solution to your problem is to define one function, save the reference to it, and use that same function for both adding and removing the listener:

var listener = function(){ Fabogore.Load();};
var listenerTab = window.gBrowser.selectedTab;
listenerTab.addEventListener("load", listener, true);
[...]
listenerTab.removeEventListener("load", listener, true);

It's important to note that I also saved the value of window.gBrowser.selectedTab in a variable. This ensures that when you remove the listener, it is from the same tab where you added it initially, preventing any confusion if the selected tab changes.

Challenges encountered with the "load" event handler when creating a Firefox Extension

Answer №1

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