event-handling | 易学教程

How can I correctly capture and re-fire the form submit event, guaranteed?

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This is probably not your usual "How do I capture form submit events?" question. I'm trying to understand precisely how form submit events are handled by jQuery, vanilla Javascript, and the browser (IE/FF/Chrome/Safari/Opera) -- and the relationships between them. ( See my other question. ) After hours of Googling and experimenting, I still cannot come to a conclusion, either because of discord or vagueness. I'm finishing up a script which integrates with website forms so that the forms can't be submitted until an AJAX request comes back. Ideally: User fills out form Form is submitted -- but

angularJS $on event handler trigger order

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问题 I was wondering two things, in the context of angularJS event handling. How is defined the order in which handlers listening to the same event are triggered? Is it a sign of a bad design if you start wondering about this? After reading documentation on angular $on, $broadcast and $emit as well as native DOM event flow I think I understand in which order event handlers will be trigger in different scopes. The problem is when several handlers listen in the same scope ($rootScope for example)

Error in IE when manually calling event handler, given certain conditions

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问题 Preface Please note, I'm not looking for a code solution, but rather insight into why this may occur. The error occurs in IE (tested 7 & 8), but not Firefox, Chrome, Safari. Description When manually calling a function assigned to onclick , IE with throw a Error: Object doesn't support this action if all of the following conditions are met: You call the method directly via the element's on[event] property. You do not use .call() or .apply() . You pass an argument (any argument, even undefined

Do you need to remove an event handler in the destructor?

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问题 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 Dispose() method I could override. PPMM is a Singleton with the same lifetime as my application. Now in the constructor of my (WPF) UserControl , I add an event handler: public MyControl() { InitializeComponent(); // hook up to an event PPMM

Using jQuery to listen to keydown event

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问题 I want to detect when the enter key is pressed, on HTML that will be injected dynamically. To simply detect when the enter key is pressed, I can do: $('#textfield').keydown(function (e){ if(e.keyCode == 13){ console.log('Enter was pressed'); } }) This code works for on() , but I am worried it is inefficient since jQuery will check every time a key is pressed. Is there anything inefficient about this? $('body').on('keydown','#textfield', function(event) { if (event.keyCode == 13) { console.log

JavaFX. Register eventHandler in custom class

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I try register eventHandler in my custom class. I don't know what interface or methods I have to implement for having addEventHandler method in my custom class. For this reason my Model class extends Rectangle ( Rectangle class has addEventHandler mechanism). Also I don't know why assigned source object not working (please see comment in Controller class). Creating custom events I make by this tutorial: https://stackoverflow.com/a/27423430/3102393 . Project Structure Controller package sample; import javafx.event.Event; public class Controller { private Model model; public Controller() { model

Events and event handling under the hood

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I've just been working through some simple programs using SDL and it made me think back to some Java GUIs I've written. In the simple SDL programs, I have a loop that checks for any events (keypresses, mouse clicks etc...) and reacts to them. Essentially it's polling for input. In Java, you attach listeners to the GUI objects and the listeners get triggered when certain events occur. My question is, does Java just handle this polling loop in the background for us and work out things like which GUI control was clicked so that it can trigger the correct listener, or is there something more

Listening for events in a UIWebView (iOS)

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I'm trying to listen for an event (specifically a button click) from a webpage I have opened in a UIWebView in my iOS app. I know that in other languages there are ways to attach event listeners to certain web calls, but I haven't yet found a way to do it in Objective-C. I also haven't found anyone online who says it can't be done, so I decided I should ask. I saw in the documentation that you can make Objective-C calls from Javascript, but I do not have control of the webpage I am wanting to monitor. So I need a solution that allows me to listen for this event entirely in Objective-C. EDIT:

C# delegate v.s. EventHandler

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问题 I want to send an alert message to any subscribers when a trap occurred. The code I created works fine using a delegate method myDelegate del . My questions are: I want to know whether it's better to use EventHandler instead of a delegate? I'm not sure what the differences are between a delegate and an EventHandler in my case. notify(trapinfo t) , that's what I've done here to get trap information. But it seems not to be a good idea. I read some online tutorial lesson introducing passing

JavaScript click handler not working as expected inside a for loop [duplicate]

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问题 This question already has answers here : How do JavaScript closures work? (86 answers) Closed 5 years ago . I'm trying to learn JS and got an issue. I tried many things and googled but all in vain. Following piece of code doesn't work as expected. I should get value of i on click but it always returns 6. I'm pulling my hair out., please help. for (var i = 1; i < 6; i++) { console.log(i); $("#div" + i).click( function() { alert(i); } ); } jsfiddle 回答1: Working DEMO This is a classic JavaScript