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How do I programmatically force an onchange event on an input?
I've tried something like this:
var code = ele.getAttribute('onchange');
eval(code);
But my end goal is to fire any listener functions, and that doesn't seem to work. Neither does just updating the 'value' attribute.
Create an Event object and pass it to the dispatchEvent method of the element:
var element = document.getElementById('just_an_example');
var event = new Event('change');
element.dispatchEvent(event);
This will trigger event listeners regardless of whether they were registered by calling the addEventListener method or by setting the onchange property of the element.
By default, events created and dispatched like this don't propagate (bubble) up the DOM tree like events normally do.
If you want the event to bubble, you need to pass a second argument to the Event constructor:
var event = new Event('change', { bubbles: true });
Information about browser compability:
dispatchEvent()
Event()
In jQuery I mostly use:
$("#element").trigger("change");
ugh don't use eval for anything. Well, there are certain things, but they're extremely rare.
Rather, you would do this:
document.getElementById("test").onchange()
Look here for more options:
http://jehiah.cz/archive/firing-javascript-events-properly
For some reason ele.onchange() is throwing a "method not found" expception for me in IE on my page, so I ended up using this function from the link Kolten provided and calling fireEvent(ele, 'change'), which worked:
function fireEvent(element,event){
if (document.createEventObject){
// dispatch for IE
var evt = document.createEventObject();
return element.fireEvent('on'+event,evt)
}
else{
// dispatch for firefox + others
var evt = document.createEvent("HTMLEvents");
evt.initEvent(event, true, true ); // event type,bubbling,cancelable
return !element.dispatchEvent(evt);
}
}
I did however, create a test page that confirmed calling should onchange() work:
<input id="test1" name="test1" value="Hello" onchange="alert(this.value);"/>
<input type="button" onclick="document.getElementById('test1').onchange();" value="Say Hello"/>
Edit: The reason ele.onchange() didn't work was because I hadn't actually declared anything for the onchange event. But the fireEvent still works.
Taken from the bottom of QUnit
function triggerEvent( elem, type, event ) {
if ( $.browser.mozilla || $.browser.opera ) {
event = document.createEvent("MouseEvents");
event.initMouseEvent(type, true, true, elem.ownerDocument.defaultView,
0, 0, 0, 0, 0, false, false, false, false, 0, null);
elem.dispatchEvent( event );
} else if ( $.browser.msie ) {
elem.fireEvent("on"+type);
}
}
You can, of course, replace the $.browser stuff to your own browser detection methods to make it jQuery independent.
To use this function:
var event;
triggerEvent(ele, "change", event);
This will basically fire the real DOM event as if something had actually changed.
This is the most correct answer for IE and Chrome::
var element = document.getElementById('xxxx');
var evt = document.createEvent('HTMLEvents');
evt.initEvent('change', false, true);
element.dispatchEvent(evt);
If you add all your events with this snippet of code:
//put this somewhere in your JavaScript:
HTMLElement.prototype.addEvent = function(event, callback){
if(!this.events)this.events = {};
if(!this.events[event]){
this.events[event] = [];
var element = this;
this['on'+event] = function(e){
var events = element.events[event];
for(var i=0;i<events.length;i++){
events[i](e||event);
}
}
}
this.events[event].push(callback);
}
//use like this:
element.addEvent('change', function(e){...});
then you can just use element.on<EVENTNAME>() where <EVENTNAME> is the name of your event, and that will call all events with <EVENTNAME>
The change event in an input element is triggered directly only by the user. To trigger the change event programmatically we need to dispatch the change event.
The question is Where and How?
"Where" we want the change event to be triggered exactly at the moment after a bunch of codes is executed, and "How" is in the form of the following syntax:
const myInput = document.getElementById("myInputId");
function myFunc() {
//some codes
myInput.dispatchEvent(new Event("change"));
}
In this way, we created the change event programmatically by using the Event constructor and dispatched it by the dispatchEvent() method. So whenever myFunc() method is invoked, after the //some codes are executed, our synthetic change event is immediately triggered on the desired input element.
Important result: Here, the change event is triggered by executing the //some codes in myFunc() instead of changing the input value by the user (default mode).
if you're using jQuery you would have:
$('#elementId').change(function() { alert('Do Stuff'); });
or MS AJAX:
$addHandler($get('elementId'), 'change', function(){ alert('Do Stuff'); });
Or in the raw HTML of the element:
<input type="text" onchange="alert('Do Stuff');" id="myElement" />
After re-reading the question I think I miss-read what was to be done. I've never found a way to update a DOM element in a manner which will force a change event, what you're best doing is having a separate event handler method, like this:
$addHandler($get('elementId'), 'change', elementChanged);
function elementChanged(){
alert('Do Stuff!');
}
function editElement(){
var el = $get('elementId');
el.value = 'something new';
elementChanged();
}
Since you're already writing a JavaScript method which will do the changing it's only 1 additional line to call.
Or, if you are using the Microsoft AJAX framework you can access all the event handlers via:
$get('elementId')._events
It'd allow you to do some reflection-style workings to find the right event handler(s) to fire.
Using JQuery you can do the following:
// for the element which uses ID
$("#id").trigger("change");
// for the element which uses class name
$(".class_name").trigger("change");
For triggering any event in Javascript.
document.getElementById("yourid").addEventListener("change", function({
//your code here
})
I'm building a file uploader plugin for studying purposes, and I'm struggling trying to get my callback working the way I want to. Briefly, this widget opperates on an input field with the type file. A little of code to explain better:
$.widget('ultimatum.uploadify', {
create: function() {
// Irrelevant code here
},
_onChange: function(event) {
// Private function that is fired when an "change" event
// is triggered by the input.
var files = event.target.files;
var fileInfo = {};
// When the file processing finish, I want to trigger this custom event:
this._trigger("fileready", null, fileInfo);
}
});
Ok, doing this way, I can handle the callback like so:
$('#upload-files').uploadify({
fileready: function(event, file) {
// My code here
}
});
The problem is that I want to handle this event like so:
$('#upload-files').uploadify();
$('.upload-files').on('fileready', function(event, file) {
// My code here.
});
Although the former way works perfectly well, the latter doesn't. Is it possible to handle custom jQuery events this way, using "on"?
From http://api.jqueryui.com/jQuery.widget/
Events
All widgets have events associated with their various behaviors to notify you when the state is changing. For most widgets, when the events are triggered, the names are prefixed with the widget name and lowercased. For example, we can bind to progressbar's change event which is triggered whenever the value changes.
$( "#elem" ).bind( "progressbarchange", function() {`
alert( "The value has changed!" );
});
Each event has a corresponding callback, which is exposed as an option. We can hook into progressbar's change callback instead of binding to the progressbarchange event, if we want to.
$( "#elem" ).progressbar({
change: function() {
alert( "The value has changed!" );
}
});
All widgets have a create event which is triggered upon instantiation.
So for your widget, this would look like:
$('#upload-files').uploadify();
$('#upload-files').on('uploadifyfileready', function(event, file) {
// My code here.
});
As I mentioned in the comment, I think that $('.upload-files') may be a typo, and that the proper selector is $('#upload-files').
I'm currently attempting to test some code that uses drag-and-drop. I found some other questions that were kinda related to this, but they were way too specific to help me, or not related enough.
This being a test, I'm struggling on trying to automatically execute code inside a .on('drop',function(e){....} event. The main issue is not that I can't run the code inside, but it's that I can't transfer the dataTransfer property, and I can't seem to fake it because it's read-only. Is there anyway to fake the dataTransfer property or otherwise get around it?
I came up with this JSFiddle that serves as a template of what I'm trying to do: https://jsfiddle.net/gnq50hsp/53/
Essentially if you are able to explain to me (if this is at all possible) how I can possibly fake the dataTransfer property, I should be all set.
Side notes:
I'm totally open to other ways of somehow getting inside that code, like for example, maybe its possible to trigger the event and pass in a fake event object with a fake dataTransfer object.
To see the drag-drop behavior, change the JavaScript load type from no-wrap head to on-Load, then you should see what I'm trying to simulate.
Important to note that I cannot modify any of the code inside the event handlers, only inside the outside function
Using Karma/Jasmine so use of those tools are also possible like spies
Also, I'm using Chrome.
Thanks in advance, and let me know for any questions/clarifications!
You should be able to override pretty much everything you want using Object.defineProperty. Depending on what you want to test it can be very simple or very complex. Faking the dataTransfer can be a bit tricky, since there's a lot of restrictions and behaviors linked to it, but if you simply want to test the drop function, it's fairly easy.
Here's a way, this should give you some ideas as to how to fake some events and data:
//Event stuff
var target = $('#target');
var test = $('#test');
test.on('dragstart', function(e) {
e.originalEvent.dataTransfer.setData("text/plain", "test");
});
target.on('dragover', function(e) {
//e.dataTransfer.setData('test');
e.preventDefault();
e.stopPropagation();
});
target.on('dragenter', function(e) {
e.preventDefault();
e.stopPropagation();
});
//What I want to simulate:
target.on('drop', function(e) {
console.log(e)
//Issue is that I can't properly override the dataTransfer property, since its read-only
document.getElementById('dataTransferDisplay').innerHTML = e.originalEvent.dataTransfer.getData("text");
});
function simulateDrop() {
// You'll need the original event
var fakeOriginalEvent = new DragEvent('drop');
// Using defineProperty you can override dataTransfer property.
// The original property works with a getter and a setter,
// so assigning it won't work. You need Object.defineProperty.
Object.defineProperty(fakeOriginalEvent.constructor.prototype, 'dataTransfer', {
value: {}
});
// Once dataTransfer is overridden, you can define getData.
fakeOriginalEvent.dataTransfer.getData = function() {
return 'test'
};
// TO have the same behavior, you need a jquery Event with an original event
var fakeJqueryEvent = $.Event('drop', {
originalEvent: fakeOriginalEvent
});
target.trigger(fakeJqueryEvent)
}
https://jsfiddle.net/0tbp4wmk/1/
As per jsfiddel link you want to achieve drag and drop feature. jQuery Draggable UI already provides this feature why you can not use that?
For create custom event on your way you have to follow two alternative ways
$('your selector').on( "myCustomEvent", {
foo: "bar"
}, function( event, arg1, arg2 ) {
console.log( event.data.foo ); // "bar"
console.log( arg1 ); // "bim"
console.log( arg2 ); // "baz"
});
$( document ).trigger( "myCustomEvent", [ "bim", "baz" ] );
On above example
In the world of custom events, there are two important jQuery methods: .on() and .trigger(). In the Events chapter, we saw how to use these methods for working with user events; for this chapter, it's important to remember two things:
.on() method takes an event type and an event handling function as arguments. Optionally, it can also receive event-related data as its second argument, pushing the event handling function to the third argument. Any data that is passed will be available to the event handling function in the data property of the event object. The event handling function always receives the event object as its first argument.
.trigger() method takes an event type as its argument. Optionally, it can also take an array of values. These values will be passed to the event handling function as arguments after the event object.
Here is an example of the usage of .on() and .trigger() that uses custom data in both cases:
OR
jQuery.event.special.multiclick = {
delegateType: "click",
bindType: "click",
handle: function( event ) {
var handleObj = event.handleObj;
var targetData = jQuery.data( event.target );
var ret = null;
// If a multiple of the click count, run the handler
targetData.clicks = ( targetData.clicks || 0 ) + 1;
if ( targetData.clicks % event.data.clicks === 0 ) {
event.type = handleObj.origType;
ret = handleObj.handler.apply( this, arguments );
event.type = handleObj.type;
return ret;
}
}
};
// Sample usage
$( "p" ).on( "multiclick", {
clicks: 3
}, function( event ) {
alert( "clicked 3 times" );
});
On above example
This multiclick special event maps itself into a standard click event, but uses a handle hook so that it can monitor the event and only deliver it when the user clicks on the element a multiple of the number of times specified during event binding.
The hook stores the current click count in the data object, so multiclick handlers on different elements don't interfere with each other. It changes the event type to the original multiclick type before calling the handler and restores it to the mapped "click" type before returning:
I've got this piece code in a view:
//dom events -----
,events:{
'click #language-switcher input[type="radio"]': function(e){
this.current_language = $(e.target).val();
}
,'click .create-gcontainer-button': function(){
this.collection.add(new Group());
}
}
,set_events:function(){
//model events -----
this.listenTo(this.collection,'add',function(group){
var group = new GroupView({ model: group });
this.group_views[group.cid] = group;
this.groups_container.append(group.el);
EventTools.trigger("group_view:create",{ lang:this.current_language });
});
this.listenTo(this.collection,'destroy',function(model){
console.log('removing model:', model);
});
//emitter events ---
EventTools.on('group_view:clear',this.refresh_groups, this);
}//set_events
Note: set_events gets called on initialization.
Well, I don't like defining events in 2 different places, but since the docs say that events defined from the 'events' prop are bound to the element (or children of it if a selector is passed), I guess I cannot use it for other types of events. Am I correct?
I also tried to define 'events' from inside my set_events function, but for some reason that leads to a memory leak or something similar (browser gets stuck).
So another more general question could be: on a Backbone view, is there a way to define all the events in one single place?
Within a View, there are two types of events you can listen for: DOM events and events triggered using the Event API. It is important to understand the differences in how views bind to these events and the context in which their callbacks are invoked.
OM events can be bound to using the View’s events property or using jQuery.on(). Within callbacks bound using the events property, this refers to the View object; whereas any callbacks bound directly using jQuery will have this set to the handling DOM element by jQuery. All DOM event callbacks are passed an event object by jQuery. See delegateEvents() in the Backbone documentation for additional details.
Event API events are bound as described in this section. If the event is bound using on() on the observed object, a context parameter can be passed as the third argument. If the event is bound using listenTo() then within the callback this refers to the listener. The arguments passed to Event API callbacks depends on the type of event. See the Catalog of Events in the Backbone documentation for details.
Yes you can define all the events in the view initialize method, see the below example
// Add your javascript here
var View = Backbone.View.extend({
el: '#todo',
// bind to DOM event using events property
initialize: function() {
// bind to DOM event using jQuery
this.events = {
'click [type="checkbox"]': 'clicked'
};
this.$el.click(this.jqueryClicked);
// bind to API event
this.on('apiEvent', this.callback);
},
// 'this' is view
clicked: function(event) {
console.log("events handler for " + this.el.outerHTML);
this.trigger('apiEvent', event.type);
},
// 'this' is handling DOM element
jqueryClicked: function(event) {
console.log("jQuery handler for " + this.outerHTML);
},
callback: function(eventType) {
console.log("event type was " + eventType);
}
});
you can see the demo here
for your code
set_events:function(){
//dom events -----
this.events={
'click #language-switcher input[type="radio"]': function(e){
this.current_language = $(e.target).val();
}
,'click .create-gcontainer-button': function(){
this.collection.add(new Group());
}
};
//model events -----
this.listenTo(this.collection,'add',function(group){
var group = new GroupView({ model: group });
this.group_views[group.cid] = group;
this.groups_container.append(group.el);
EventTools.trigger("group_view:create",{ lang:this.current_language });
});
this.listenTo(this.collection,'destroy',function(model){
console.log('removing model:', model);
});
//emitter events ---
EventTools.on('group_view:clear',this.refresh_groups, this);
}//set_events
As I commented above, for some strange reason, placing events inside initialize() or set_events() fails silently. I found out that doing one of the 2, backbone doesn't find the events. This backbone's view's function says undefined to console:
delegateEvents: function(events) {
events || (events = _.result(this, 'events'));
console.log(events); //outputs undefined
if (!events) return this;
this.undelegateEvents();
for (var key in events) {
var method = events[key];
if (!_.isFunction(method)) method = this[method];
if (!method) continue;
var match = key.match(delegateEventSplitter);
this.delegate(match[1], match[2], _.bind(method, this));
}
return this;
},
Though, if I place events like a regular view property, just as my code on the main question, it will correctly log the events.
How do I programmatically force an onchange event on an input?
I've tried something like this:
var code = ele.getAttribute('onchange');
eval(code);
But my end goal is to fire any listener functions, and that doesn't seem to work. Neither does just updating the 'value' attribute.
Create an Event object and pass it to the dispatchEvent method of the element:
var element = document.getElementById('just_an_example');
var event = new Event('change');
element.dispatchEvent(event);
This will trigger event listeners regardless of whether they were registered by calling the addEventListener method or by setting the onchange property of the element.
By default, events created and dispatched like this don't propagate (bubble) up the DOM tree like events normally do.
If you want the event to bubble, you need to pass a second argument to the Event constructor:
var event = new Event('change', { bubbles: true });
Information about browser compability:
dispatchEvent()
Event()
In jQuery I mostly use:
$("#element").trigger("change");
ugh don't use eval for anything. Well, there are certain things, but they're extremely rare.
Rather, you would do this:
document.getElementById("test").onchange()
Look here for more options:
http://jehiah.cz/archive/firing-javascript-events-properly
For some reason ele.onchange() is throwing a "method not found" expception for me in IE on my page, so I ended up using this function from the link Kolten provided and calling fireEvent(ele, 'change'), which worked:
function fireEvent(element,event){
if (document.createEventObject){
// dispatch for IE
var evt = document.createEventObject();
return element.fireEvent('on'+event,evt)
}
else{
// dispatch for firefox + others
var evt = document.createEvent("HTMLEvents");
evt.initEvent(event, true, true ); // event type,bubbling,cancelable
return !element.dispatchEvent(evt);
}
}
I did however, create a test page that confirmed calling should onchange() work:
<input id="test1" name="test1" value="Hello" onchange="alert(this.value);"/>
<input type="button" onclick="document.getElementById('test1').onchange();" value="Say Hello"/>
Edit: The reason ele.onchange() didn't work was because I hadn't actually declared anything for the onchange event. But the fireEvent still works.
Taken from the bottom of QUnit
function triggerEvent( elem, type, event ) {
if ( $.browser.mozilla || $.browser.opera ) {
event = document.createEvent("MouseEvents");
event.initMouseEvent(type, true, true, elem.ownerDocument.defaultView,
0, 0, 0, 0, 0, false, false, false, false, 0, null);
elem.dispatchEvent( event );
} else if ( $.browser.msie ) {
elem.fireEvent("on"+type);
}
}
You can, of course, replace the $.browser stuff to your own browser detection methods to make it jQuery independent.
To use this function:
var event;
triggerEvent(ele, "change", event);
This will basically fire the real DOM event as if something had actually changed.
This is the most correct answer for IE and Chrome::
var element = document.getElementById('xxxx');
var evt = document.createEvent('HTMLEvents');
evt.initEvent('change', false, true);
element.dispatchEvent(evt);
If you add all your events with this snippet of code:
//put this somewhere in your JavaScript:
HTMLElement.prototype.addEvent = function(event, callback){
if(!this.events)this.events = {};
if(!this.events[event]){
this.events[event] = [];
var element = this;
this['on'+event] = function(e){
var events = element.events[event];
for(var i=0;i<events.length;i++){
events[i](e||event);
}
}
}
this.events[event].push(callback);
}
//use like this:
element.addEvent('change', function(e){...});
then you can just use element.on<EVENTNAME>() where <EVENTNAME> is the name of your event, and that will call all events with <EVENTNAME>
The change event in an input element is triggered directly only by the user. To trigger the change event programmatically we need to dispatch the change event.
The question is Where and How?
"Where" we want the change event to be triggered exactly at the moment after a bunch of codes is executed, and "How" is in the form of the following syntax:
const myInput = document.getElementById("myInputId");
function myFunc() {
//some codes
myInput.dispatchEvent(new Event("change"));
}
In this way, we created the change event programmatically by using the Event constructor and dispatched it by the dispatchEvent() method. So whenever myFunc() method is invoked, after the //some codes are executed, our synthetic change event is immediately triggered on the desired input element.
Important result: Here, the change event is triggered by executing the //some codes in myFunc() instead of changing the input value by the user (default mode).
if you're using jQuery you would have:
$('#elementId').change(function() { alert('Do Stuff'); });
or MS AJAX:
$addHandler($get('elementId'), 'change', function(){ alert('Do Stuff'); });
Or in the raw HTML of the element:
<input type="text" onchange="alert('Do Stuff');" id="myElement" />
After re-reading the question I think I miss-read what was to be done. I've never found a way to update a DOM element in a manner which will force a change event, what you're best doing is having a separate event handler method, like this:
$addHandler($get('elementId'), 'change', elementChanged);
function elementChanged(){
alert('Do Stuff!');
}
function editElement(){
var el = $get('elementId');
el.value = 'something new';
elementChanged();
}
Since you're already writing a JavaScript method which will do the changing it's only 1 additional line to call.
Or, if you are using the Microsoft AJAX framework you can access all the event handlers via:
$get('elementId')._events
It'd allow you to do some reflection-style workings to find the right event handler(s) to fire.
Using JQuery you can do the following:
// for the element which uses ID
$("#id").trigger("change");
// for the element which uses class name
$(".class_name").trigger("change");
For triggering any event in Javascript.
document.getElementById("yourid").addEventListener("change", function({
//your code here
})