Develop Reference

Detecting Special Key Presses in Javascript

I have an input box and want to adjust the value when a key is pressed.
'keypress .comment-input': 'onCommentInputKeyBlur',
When a key is pressed, a class is added to the html element to reflect the changes.
onCommentInputKeyBlur: function(ev) {
var $form = $('#comment-submit');
if (ev.which) {
$form.addClass('focused');
} else if (!$(ev.currentTarget).val()) {
$form.removeClass('focused');
}
},
However, this doesn't detect special keys being pressed (ie when a user presses ctrl+v for a paste, it's not detected and the formatting is therefore wrong).
Using keyup and keydown halfway solve the problem, but formatting is wrong for a brief second:
Keydown -> the value isn't supposed to change until an actual value is entered through a keypress, but it changes right when ctrl is hit instead of waiting for the second key
Keyup -> new value is briefly pasted over the previous one while waiting for the key to actually be released.
Is there a better way to about solving this? Ideally, I would like to detect if the key entered does actually produce a value and is not simply a special key.

Look into the onchange event. It is fairly well supported and may solve your problem.

What is the ultimate goal of this functionality? perhaps there is a better approach.
If you insist on doing this via keypress event, then you can simply check event.keyCode and filter out the few keycodes that dont change anything, such as shift, control, alt.

how to create a new text field below when pressing a key?

last.fm has this nifty feature when you're adding an event. you have the Artists field, and when you start typing in it, another text field appears beneath it. when you start typing in that next field, another new field appears beneath and so on. I've been trying to figure out how to mimic this functionality using jquery but I can make it work on the first, stationary, field only. any ideas?
edit:
actually, nope, it's not working even for the stationary one, since it adds the field on EVERY key press
edit2:
alrighty, so some fine folks have already solved my adding issue, now, how would one go about adding the field only after the first time a key is pressed.

You are probably only binding your handler to the first static input, and not the dynamically created ones. Use .live() to do your event binding. That will bind the event to future elements that match the selector.
To make sure you only add one new one, make sure you only add it when typing into the last textbox. Check $(this).closest(".container").next(".container").length to make sure there isn't already a new textbox.
$("input.myClass").live("keyup", function (e) {
var $container = $(this).closest(".container");
if (this.value && !$container.next(".container").length) {
var $newContainer $("<div>").insertAfter($container).addClass("container");
...
}
});

Live is the right idea but closest is overkill: jsFiddle
$("input").live("keyup", function (){
if ( !$(this).next('input').length ) $(this).after('<input type="text"></input>');
});

how to check if the value of a text input is empty right after the keypress event in javascript?

Here's the problem, in abstract terms: i have three input fields (A, B, C). two of them need to be text inputs (A and B), the third is of irrelevant type. I need to enable the third if A is not empty and B is not empty. I need to disable C if A is empty or B is empty.
The code
// empty is the empty function from the phpjs project
// framework used: jQuery
// A, B and C are classes here
$(".A, .B").keypress(function(){
if( !empty($(".A").val()) && !empty($(".B").val()) )
$(".C").attr("disabled","");
else
$(".C").removeAttr("disabled");
});
I want to be able to check this on keypress, but when requesting the value of the input that is edited when the keypress event occurs i get the value that was calculated before the keypress event.
Has anybody stumbled upon this before and solved it?

have you tried using the keyUp event?

Use the keyup event instead.

Attach your handler to the keyrelease event. The value should have been updated by then.

use a combination of handlers for keyup and change. the keyup handler will update as the user types (excepting edge cases like holding a key down, which doesn't seem like a concern here) and the change handler will catch things like the user cutting the text with mouse actions before they can switch to field C. as an added measure you could add verification on field C's focus event, to make sure A and B really have something.

$('.A, .B').keydown(function(event) {
if(!empty($('.A').val()) && !empty($('.B').val()))
$(".C").attr("disabled","");
else
$(".C").removeAttr("disabled");
});

At the keypress event, the value of the INPUT is not yet set. Hence you can't easily know if it is empty.
While the keyup fires, the value of the INPUT is set.
But things get worse. The user can empty the field with the mouse or the Edit menu of the browser. In that case keyup is not fired.
In our web app we auto-save the values. Like in Mac OS, if you know, there is almost no save buttons.
To allow a reaction here is more or less what we do:
onfocus: a setInterval starts polling every 120ms or so, and checks the input for any change
if there is a change do the relevant action
onblur: a clearInterval stop the polling

showing divs using keyboard commands

is it possible to show/hid a div on a webpage if say three keys are pressed in the correct order on a normal keyboard....
Im trying to hide my login div in drupal and only want it to show if I press say three keys on the keyboard. Dosnt matter if it shows up in source.
any thoughts/links?
cheers

You can try js-hotkeys.
jQuery.Hotkeys plugin lets you easily add and remove handlers for keyboard events anywhere in your code supporting almost any key combination. It takes one line of code to bind/unbind a hot key combination.
Example: Binding 'Ctrl+c'
$(document).bind('keydown', 'ctrl+c', fn);
Next step is to show/hide your div in the function you pass in.

You have to intercept the keypress event (or keyup) and then check which key was pressed (see jQuery Event Keypress: Which key was pressed?)
To handle a key sequence you have to store the pressed key codes into an array and then check it against your defined sequence.

This "cheat code" jQuery plugin should make what you're asking especially simple.

If you poll for key presses and store them in array then match that with the correct array once this happens show the div then clear your stored array. Close the div and start the process again.

Jquery Keypress is not working for my input box

$("#epFilter").keypress(function(){
query = $("#epFilter").val();
alert(query);
});
In this code, whenever I type in my text box, it always alert one character less. It doesn't catch the last character. Why?

Use the keyup event instead.
$("#epFilter").keyup(function(){
query = $("#epFilter").val();
alert(query);
});

keypress event is triggered when user presses a key, but before the character is inserted. Use keyup event instead.

Slightly improving Matt's answer (using this inside event handler):
$("#epFilter").keyup(function(){
query = $(this).val();
alert(query);
});

I wonder if that is a "normal" behavior. Shouldn't keypress be similar to keydown+keyup (except for the codes and keys)?
I had the same problem. I have an input-text field and I want to calculate a total on keypress. However, it does not change the total until I input again another character (this means when I entered the first digit it didn't update). I used "keyup" and was "fixed", but I think it could be better if I use keypress as it doesn't fire when I press other keys (like Ctrl, Shift, arrows, etc).
According to the documentation Keypress should work as I expected but for some reason it didn't.
This is not exactly an answer (so don't vote for it). Just my contribution.