In the following code, copied from ch 15 of Eloquent Javascript, how does pressed[codes[event.keyCode]] end up as a boolean value? I just can’t figure out why you need the ‘keyup’ event listener. The idea is to make sure that ‘keydown’ gets registered only once when it is being h…
Tag: event-handling
Remove custom event listener
I’m listening to a custom event: I need to remove the listener. I’ve tried: but neither work. What am I doing wrong? Answer The third argument to removeEventListener is mandatory. try this:
Do JavaScript bindings take up memory while not in use?
I have a calendar that I’ve built, and on clicking a day on the calendar, a function is run. You can go month to month on the calendar, and it generates months as it goes. Since every day on the calendar, shown or not, is binded to an event using the class of all the “days,” I’m worrie…
What does it mean by “message queue” in this link?
I was trying to understand what’s an event loop in JavaScript. Came across Mozilla Developer Network’s link about event loop. https://developer.mozilla.org/en-US/docs/Web/JavaScript/Guide/EventLoop It mentions Queue A JavaScript runtime contains a message queue, which is a list of messages to be p…
What version of IE doesn’t pass the event as argument to listeners?
As some old versions of IE didn’t provide the event as argument to event listeners, we got used to (event||window.event). In order to decide whether it can still make some sense to have this in a modern library, I tried to look at what versions were concerned but I couldn’t find this information. …
How to create a single event handler for a variety of events in JavaScript
I want to do the following with JavaScript/jQuery: JavaScript Pseudo code! HTML Someone knows where to start? It has to be AJAX proof just like the jQuery $.on() method. I only want this for a variety of events and bind it to elements containing the action attribute. Maybe I just parse the HTML and then dynam…
On an EventEmitter, how can I know all the events I can listen to?
Supposing I have an object that inherited from EventEmitter, like a stream or any other, is there a good way to know all the events I can listen to, and all the attached event listeners ? I think the second part of the question is easy, emitter.listeners(event) will tell me all the listeners to an event. But …
Dynamically disabling/enabling jquery click handlers using delegated events
I have a number of clickable elements on a page that shouldn’t be enabled until a resource gets loaded. My idea was to initialize the buttons with a .disabled class, which I would then remove when the resource was ready. In the meantime, I’d have a handler on the .disabled click event that would p…
When is an event.target.value not a string?
I came accross value = String(event.target.value || “”) when a textinputs keyup/keydown event is fired. But i’m not sure when the event.target.value is not a string? Is this possible? When is something else passed off as an event.target.value? Answer If the event.target element is not an inp…
How can I make an element trigger a function on any, and all events?
I don’t think an explanation of my specific scenario would help much here. So in short I need to know how I can call a function on any and all events. The idea is to call the same function no matter what event happens to a specific element. In my head the ideal way to do this would go something