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Questions tagged [event-handling]

Event handling is a coding style about handling messages between a source and one or more subscribers. A point listener in the source provide a way which subscribed code can consume messages raised from the source.

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event.preventDefault() vs. return false (no jQuery)

I wondered if event.preventDefault() and return false were the same. I have done some tests, and it seems that If the event handler is added using old model, for example elem.onclick = function(){ return false; }; Then, return false prevents…
Oriol
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Handle URL fragment identifier (anchor) change event in Javascript

How can I write the Javascript callback code that will be executed on any changes in the URL fragment identifier (anchor)? For example from http://example.com#a to http://example.com#b
Bogdan Gusiev
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How to removeEventListener that is addEventListener with anonymous function?

function doSomethingWith(param) { document.body.addEventListener( 'scroll', function() { document.write(param); }, false ); // An event that I want to remove later } setTimeout( …
Japboy
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How to trigger function on value change?

I realise this question has to do with event-handling and i've read about Python event-handler a dispatchers, so either it did not answer my question or i completely missed out the information. I want method m() of object A to be triggered whenever…
neydroydrec
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How do I make an Event in the Usercontrol and have it handled in the Main Form?

I have a custom usercontrol and I want to do something relatively simple. When ever a numeric up down in that usercontrol's value changes, have the main form update a display window. This is not a problem if the NUD was not in a usercontrol but I…
Crash893
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How to distinguish between move and click in onTouchEvent()?

In my application, I need to handle both move and click events. A click is a sequence of one ACTION_DOWN action, several ACTION_MOVE actions and one ACTION_UP action. In theory, if you get an ACTION_DOWN event and then an ACTION_UP event - it means…
some.birdie
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Difference between event handlers and callbacks

What is the difference between an event handler and a callback function?
Aaron S
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jQuery change method on input type="file"

I'm trying to embrace jQuery 100% with it's simple and elegant API but I've run into an inconsistency between the API and straight-up HTML that I can't quite figure out. I have an AJAX file uploader script (which functions correctly) that I want to…
gurun8
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.NET Events - What are object sender & EventArgs e?

What do sender and eventArgs mean/refer to? How can I make use of them (for the scenario below)? Scenario: I'm trying to build a custom control with a delete function, and I want to be able to delete the control that was clicked on a page that…
stringo0
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What is an "event emitter"?

Browsing through http://microjs.com, I see lots of libraries labelled "event emitters". I like to think I know my way around the basics of the Javascript language pretty well, but I really have no idea what an "event emitter" is or does. Anyone…
wwaawaw
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C#: Difference between ' += anEvent' and ' += new EventHandler(anEvent)'

Take the below code: private void anEvent(object sender, EventArgs e) { //some code } What is the difference between the following ? [object].[event] += anEvent; //and [object].[event] += new EventHandler(anEvent); [UPDATE] Apparently,…
Andreas Grech
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How to overwrite jquery event handlers

I'll try to explain the problem with a simple code. var fireClick = function() { alert('Wuala!!!') }; $('#clickme').click(fireclick); $('#clickme').click(fireclick); So now it will obviously alert 2 times but i need it alert only once. Tried so…
taras
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Difference between the KeyDown Event, KeyPress Event and KeyUp Event in Visual Studio

Can anyone tell me the difference between the KeyDown event, the KeyPress event and the KeyUp event? I checked the msdn site and it does not explain it much. Can anyone tell me in simple logical sense when each of the event occurs? I feel that all…
reggie
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Is it bad practice to write inline event handlers

Is it bad practice to write inline event handlers ? For me, I prefer use it when I want to use a local variable in the event handler like the following: I prefer this: // This is just a sample private void Foo() { Timer timer = new Timer() {…
Homam
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Do you need to remove an event handler in the destructor?

I use some UserControls which get created and destroyed within my application during runtime (by creating and closing subwindows with these controls inside). It's a WPF UserControl and inherits from System.Windows.Controls.UserControl. There is no…
Martin Hennings
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