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Virtual Keyboard with Jquery

I have a div that operates as a button. Once the button is clicked, I want it to simulate the pressing of a key. Elsewhere on Stackoverflow, people have suggested using jQuery.Event("keydown"); but the suggestions all use a .trigger() bound to the button as opposed to .click. So, my example code looks like this:
var press = jQuery.Event("keydown");
press.which = 69; // # The 'e' key code value
press.keyCode = 69;
$('#btn').click( function() {
$('#testInput').focus();
$(this).trigger(press);
console.info(press);
});
I've set up a dummy example at JSFiddle:
http://jsfiddle.net/ruzel/WsAbS/
Eventually, rather than have the keypress fill in a form element, I just want to register the event as a keypress to the document so that a MelonJS game can have it.
UPDATE: It looks like triggering a keypress with anything other than the keyboard is likely to be ignored by the browser for security reasons. For updating a text input, this very nice Jquery plugin will do the trick: http://bililite.com/blog/2011/01/23/improved-sendkeys/
As for anyone who comes here looking for the solution in the MelonJS case, it's best to use MelonJS's me.input object, like so:
$('#btn').mousedown(function() {
me.input.triggerKeyEvent(me.input.KEY.E, true);
});
$('#btn').mouseup(function() {
me.input.triggerKeyEvent(me.input.KEY.E, false);
});

I'm not sure why, but even though this is triggering the event correctly, it doesn't fill the input with the character.
I've modified the code to show that the document is indeed receiving keypress events when we say $(document).trigger(p)
Try it out:
http://jsfiddle.net/WsAbS/3/
var press = jQuery.Event("keydown");
press.which = 69; // # Some key code value
press.keyCode = 69;
press.target = $('#testInput');
$(document).on('keydown', function(event) {
alert(event.keyCode);
});
$('#btn').click( function() {
$(document).trigger(press);
});
I believe this should be good enough for your end goal of a MelonJS game picking up keypresses.

If you want a virtual keyboard (As the title suggests) you can use this one.

jQuery bind to keyup only, not focus

This seems like a simple thing but google hasn't turned up anything for me:
How can I bind to a text / value change event only, excluding an input gaining focus? Ie, given the following:
$(function(){
$('input#target').on('keyup', function(){
alert('Typed something in the input.');
});
});
...the alert would be triggered when the user tabs in and out of an element, whether they actually input text or not. How can you allow a user to keyboard navigate through the form without triggering the event unless they input/change the text in the text field?
Note: I'm showing a simplified version of a script, the reason for not using the change event is that in my real code I have a delay timer so that the event happens after the user stops typing for a second, without them having to change focus to trigger the event.

Store the value, and on any key event check if it's changed, like so:
$(function(){
$('input#target').on('keyup', function(){
if ($(this).data('val')!=this.value) {
alert('Typed something in the input.');
}
$(this).data('val', this.value);
});
});​
FIDDLE

Simply use the .change event.
Update: If you want live change notifications then do you have to go through the keyup event, which means that you need to program your handler to ignore those keys that will not result in the value being modified.
You can implement this with a whitelist of key codes that are ignored, but it could get ugly: pressing Del results in the value being changed, unless the cursor is positioned at the end of the input in which case it does not, unless there happens to be a selected range in the input in which case it does.
Another way which I personally find more sane if not as "pure" is to program your handler to remember the old value of the element and only react if it has changed.
$(function() {
// for each input element we are interested in
$("input").each(function () {
// set a property on the element to remember the old value,
// which is initially unknown
this.oldValue = null;
}).focus(function() {
// this condition is true just once, at the time we
// initialize oldValue to start tracking changes
if (this.oldValue === null) {
this.oldValue = this.value;
}
}).keyup(function() {
// if no change, nothing to do
if (this.oldValue == this.value) {
return;
}
// update the cached old value and do your stuff
this.oldValue = this.value;
alert("value changed on " + this.className);
});
});​
If you do not want to set properties directly on the DOM element (really, there's nothing wrong with it) then you could substitute $(this).data("oldValue") for this.oldValue whenever it appears. This will technically have the drawback of making the code slower, but I don't believe anyone will notice.
See it in action.

This will do it, set a custom attribute and check against that:
$('input').focus(function(){
$(this).attr('originalvalue',$(this).val());
});
$('input').on('keyup',function(){
if($(this).val()===$(this).attr('originalvalue')) return;
alert('he must\'ve typed something.');
});
Be wary of events firing multiple times.

Here is another version that plainly tests if the input field is empty.
If the input is empty then the action is not performed.
$(function(){
$(selector).on('keyup', function(){
if ($(this).val()!='') {
alert('char was entered');
}
})
});

Change event precedence with JQuery

I have the following html code:
<input type="text" id="theInput" value=""/>
Click me
I want to detect when the input changes and perform an operation in this case, but ONLY when the user has not clicked in the link. I have tried this:
$('#theLink').live('click', function(){
alert('click');
});
$('#theInput').live('change', function(){
alert('change');
});
However change is always executed before click when the value in the input changed, due to Javascript event precedence rules, and therefore only "change" message is displayed.
I would like it to display change only if the input value changed and the user exited the input clicking in any other place instead of the link. In that last case I would like to display click.
The example is here.
I use jQuery 1.6.4.

As far as I know, the click event fires after the blur and change events in every browser (have a look at this JSFiddle). The order of blur and change is different across browsers (source: Nicholas Zakas).
To solve your problem, you could listen to click events on the document and compare the event's target with #theLink. Any click event will bubble up to the document (unless it is prevented).
Try this:
var lastValue = '';
$(document).click(function(event) {
var newValue = $('#theInput').val();
if ($(event.target).is('#theLink')) {
// The link was clicked
} else if (newValue !== lastValue) {
// Something else was clicked & input has changed
} else {
// Something else was clicked but input didn't change
}
lastValue = newValue;
});
JSFiddle: http://jsfiddle.net/PPvG/TTwEG/

Both events will fire but in your example the alert in the onchange event handler fired when the onmousedown event occurs will stop the onmouseup event required for the onclick event to fire. Using console.log will show both events firing.
http://jsfiddle.net/hTqNr/4/

Ok, now i got it, you could do
$('#theLink').live('click', function(e){
alert('click');
});
$('#theInput').live('change', function(e){
//Check if the change events is triggerede by the link
if(e.originalEvent.explicitOriginalTarget.data === "Click me"){
//if this is the case trigger the click event of the link
$('#theLink').trigger("click");
}else{
//otherwise do what you would do in the change handler
alert('change');
}
});
Fiddle here http://jsfiddle.net/hTqNr/19/

why you dont pick the value of input box. you have to store initial value of input box on ready function
initialvalue= $('#theInput').val();
then compare the value
$('#theLink').live('click', function(){
var newvalue =$('#theInput').val();
if(newvalue!=initialvalue) {
//do something
}
});

How to trigger backspace on a textfield?

Say I have this:
<textarea id="myarea">Hello</textarea>
How would i trigger backspace on that textarea possibly using trigger() and key codes. The code for backspace is 8.
And i am not looking for this:
$('#myarea').val( $("myarea").val().slice(0,-1) );
I need to simulate someone actually pressing the 'backspace' key on their keyboard.
Thanks

You can create a keydown event:
var e = jQuery.Event("keydown", { keyCode: 20 });
Then trigger it in your textarea:
$("#myarea").trigger( e );
Update:
After doing some more research and testing, I realize that this solution does NOT simulate a natural keypress event on the HTML element. This method only triggers the keydown event, it does not replicate the user going into the element and pressing that key.
To simulate the user going into that textbox and pressing that key, you would have to create a dispatch event
The dispatch event is also not globally supported. Your best bet would be to trigger the keydown event and then update the text area as intended.

I found this:
http://forum.jquery.com/topic/simulating-keypress-events (answer number 2).
Something like this should work, or at least give you an idea:
<div id="hola"></div>
$(function(){
var press = jQuery.Event("keyup");
press.ctrlKey = false;
press.which = 40;
$('#hola').keyup(function(e){
alert(e.which);
})
.trigger(press); // Trigger the event
});
Demo: http://jsfiddle.net/qtPcF/1/

You shouldn't be forcing key events in js. Try simulating the character removal instead.
const start = textarea.selectionStart - 1;
const value = textarea.value;
const newValue = value.substr(0, start) + a.substr(start);
textarea.value = newValue;
Or if you just want the event, instead call the handler directly, rather than forcing the event. This is too hacky.

Javascript virtual keyboard: how to indentify text fields?

I'm developing a Javascript virtual keyboard, and I would like it to appear everytime a user press enter on a text fields. But how can I know if a text (or any input) field is selected?
--clarification
I have to information or control over the page that will be loaded. I just want that, if a input field is selected and the user press enter, my virtual keyboard shows up.
--update
Does it makes any difference if what I'm trying to do is a firefox extension? (I think it shouldn't)

use jQuery and add the following
$(document).ready(function() {
//apply action to input elements by class
//$("#.input_class").keypress(function(e) {
//apply action to all input elements ( input, textarea, select and button )
$(':input').keypress(function(e) {
if(e.keyCode==13){
// Enter pressed... do anything here...
alert($(this).val());
} else {
//make shure you get the desired action for other keys pressed
xTriggered++;
}
//do not submit the form
return false;
});
});

bind it to the onfocus event. That event is triggered when the input element gets the focus. You could remove the keyboard again on the onblur event if you want to hide it again.

To get notified that a text field is selected, you could attach an event handler to onfocus of the fields you're interested in.
Example in jQuery (jQ chosen for brevity, the event works in plain JS):
$('input[type="text"]').focus(function(event){
// do something here
});
If you only care to capture the "enter" key, you don't need to worry about focus, just attach to the onkeypress event of the textfields (see #poelinca's answer).

Despite of what jquery apologetes say, there is no hassle to instrument all fields without resorting to large and slow external library:
for (var i = 0; i < document.forms.length; i++)
for (var j = 0; j < document.forms[i].elements.length; j++)
if (document.forms[i].elements[j].tagName.match(/^INPUT$/i))
if (document.forms[i].elements[j].type.match(/^TEXT$/i))
document.forms[i].elements[j].addEventListener('focus', function(){/* your stuff here */}, false);

My solution, for now, was use a specified key just to open the virtual keyboard when the user request.