I'm trying to catch the value of an input element every time its value changed. change requires blurring the element so it is not good for my case. I came across this Javascript change event on input element fires on only losing focus question and the accepted answer solved my problem, partly. According to the fiddle the event I should be watching is
$('#name').bind('DOMAttrModified textInput input change keypress paste focus', function () {
.....
})
However it doesn't work so well with characters that require an input method to input. For example, to input Chinese character "長", I'd press "c","h","a","n",“g” and then "space", all these keystrokes are recorded and will fire the events unwantedly - I only want to catch "長" as the input value, and the trigger should only fire when this character appears in the input textbox.
I've tried different combinations of the events, but none of them works. Is there any way to work this around?
I've added an on 'change' event listener to a type=email input element. When I add a couple space characters into the email field, then lose focus on that element, the change event doesn't seem to be firing.
However, this exact scenario works just fine with type=text input elements.
What's going on?
$('input[type="email"]').change(e => {
console.log('Triggered!');
});
Browser: Chrome Version 63.0.3239.132 (Official Build) (64-bit)
I originally said that it looks like there is an automatic trim operation performed on email fields because the length of the value is coming back at 0 after typing some spaces and leaving the field, but upon returning to the field, the spaces remain in the element, so they aren't getting trimmed out.
I suspect that, because spaces are not valid for this input type, they are not considered part of the value, thus the value doesn't change when you enter them and the change event doesn't fire.
Type some spaces in the field and then hit TAB to leave the field, but then return to the field. The spaces will still be there.
$('input[type="email"]').on("blur", function(e){
console.log(this.value.length);
});
$('input[type="email"]').on("change", function(e){
console.log("Change fired!");
});
<script src="https://ajax.googleapis.com/ajax/libs/jquery/2.1.1/jquery.min.js"></script>
<input type="email">
You can use something like that:
$('input[type="email"]').on('focusout', {
console.log('Triggered!');
var $trig = $(this);
$trig.attr('trimmed', $trig.val().toString().trim());
$trig.val( '').val($trig.attr('trimmed'));
});
But, as answered above, input[type="email"] does not count whitespaces. It is only works as fast hack;
I am facing the same problem with React, and I don't want to reflect the error on the onBlur event (as other solutions here). I don't think an error should be reflected in any input by the simple fact of removing the mouse from that input. For me that's not User friendly,... AT ALL.
Why?
Because the User might have decided to remove the mouse from that
Input only because he/she simply wants to copy something from somewhere else first,... and then past it there (and/or to past it somewhere else). So technically there is no mistake there yet.
Because I simply want to fill another input field of the form first.
Why? Becase that's precisely the field's value I already copied from
somewhere else, so that's the value I have stored in clipboard, and
it doesn't goes where my mouse landed by default. Or simply because
I just want to! I'm the User, so I can choose the order to
fill the form!
For me is more than enough with validating what the User has written and/or removed/deleted from the Inputs (onChange validation) AND also what the User finally decides to send (onSubmit validation). A proper combination of onChange and onSubmit validation is the perfect healthy balance between thoroughness and User friendly.
A Solomonic "solution":
I am using a custom validation hook. As I can not change the behavior of the input with a type email regarding the white spaces in an OnChange event,... then I decided to use a workaround, which is simply avoiding the typing of white spaces and that's it, as the onChange event won't trigger anyway.
const preventWhiteSpaceOnKeyDown = (e) => {
if (e.key === " ") {
e.preventDefault();
}
}
.
.
.
<input
type={"email"}
id='commentEmail'
name='commentEmail'
required={true}
autoFocus={true}
ref={emailInputRef}
value={emailState}
onChange={emailInputChangeHandler}
onKeyDown={preventWhiteSpaceOnKeyDown}
/>
This is not a "solution". There is no clean solution for this. But after this at least my input[type=email] element won't hold useless white spaces.
input[type="email"] does not fire change event, use blur event instead:
$('input[type="email"]').blur(function(){
console.log('blur event is fired.');
});
I am currently working on a encoder. I basically have a textarea which accepts the string. When a letter is displayed using the document.onkeydown(event.keycode) I record the keystrokes and display it back on the same field. The problem arises after the onkeydown() finishes, the encrypted letter displays on the TextArea followed by the original letter.
I tried deleting the last added letter using splice or substring functions but for a fraction of a second you can see the letter or if you hold a key you can see the actual letter. So how do I hide the original input?
Is there is something similar in javascript like C's getch() where a key is pressed and no output is shown?
Thanks in advance.
The function you're looking for is preventDefault().
https://developer.mozilla.org/en-US/docs/Web/API/Event/preventDefault
So inside your event handler, you would call preventDefault on the event parameter. This prevents any default behavior from occurring, and lets you defined it yourself. In your case, this would prevent the letter pressed from being added to the input field.
For example:
function onClick(e) {
e.preventDefault();
//your code here
}
What is the difference between these three events? Upon googling I found that:
The onKeyDown event is triggered when the user presses a key.
The onKeyUp event is triggered when the user releases a key.
The onKeyPress event is triggered when the user presses & releases a key
(onKeyDown followed by onKeyUp).
I understand the first two, but isn't onKeyPress the same as onKeyUp? Is it possible to release a key (onKeyUp) without pressing it (onKeyDown)?
This is a bit confusing, can someone clear this up for me?
NOTE KeyPress is now deprecated. Use KeyDown instead.
KeyPress, KeyUp and KeyDown are analogous to, respectively: Click, MouseUp, and MouseDown.
Down happens first
Press happens second (when text is entered)
Up happens last (when text input is complete).
The exception is webkit, which has an extra event in there:
keydown
keypress
textInput
keyup
Below is a snippet you can use to see for yourself when the events get fired:
window.addEventListener("keyup", log);
window.addEventListener("keypress", log);
window.addEventListener("keydown", log);
function log(event){
console.log( event.type );
}
Check here for the archived link originally used in this answer.
From that link:
In theory, the onKeyDown and onKeyUp events represent keys being pressed or released, while the onKeyPress event represents a character being typed. The implementation of the theory is not same in all browsers.
Most of the answers here are focused more on theory than practical matters and there's some big differences between keyup and keypress as it pertains to input field values, at least in Firefox (tested in 43).
If the user types 1 into an empty input element:
The value of the input element will be an empty string (old value) inside the keypress handler
The value of the input element will be 1 (new value) inside the keyup handler.
This is of critical importance if you are doing something that relies on knowing the new value after the input rather than the current value such as inline validation or auto tabbing.
Scenario:
The user types 12345 into an input element.
The user selects the text 12345.
The user types the letter A.
When the keypress event fires after entering the letter A, the text box now contains only the letter A.
But:
Field.val() is 12345.
$Field.val().length is 5
The user selection is an empty string (preventing you from determining what was deleted by overwriting the selection).
So it seems that the browser (Firefox 43) erases the user's selection, then fires the keypress event, then updates the fields contents, then fires keyup.
First, they have different meaning: they fire:
KeyDown – when a key was pushed down
KeyUp – when a pushed button was released, and after the value of input/textarea is updated (the only one among these)
KeyPress – between those and doesn't actually mean a key was pushed and released (see below). Not only it has inconsistent semantics, it was deprecated, so one shouldn't probably use it (see also this summary)
Second, some keys fire some of these events and don't fire others. For instance,
KeyPress ignores delete, arrows, PgUp/PgDn, home/end, ctrl, alt, shift etc while KeyDown and KeyUp don't (see details about esc below);
when you switch window via alt+tab in Windows, only KeyDown for alt fires because window switching happens before any other event (and KeyDown for tab is prevented by system, I suppose, at least in Chrome 71).
Also, you should keep in mind that event.keyCode (and event.which) usually have same value for KeyDown and KeyUp but different one for KeyPress. Try the playground I've created. By the way, I've noticed quite a quirk: in Chrome, when I press ctrl+a and the input/textarea is empty, for KeyPress fires with event.keyCode (and event.which) equal to 1! (when the input is not empty, it doesn't fire at all).
Note: these days, using event.key is the most useful option as it is standardized across browsers, OSes and events (afaik).
Finally, there's some pragmatics:
For handling arrows, you'll probably need to use onKeyDown: if user holds ↓, KeyDown fires several times (while KeyUp fires only once when they release the button). Also, in some cases you can easily prevent propagation of KeyDown but can't (or can't that easily) prevent propagation of KeyUp (for instance, if you want to submit on enter without adding newline to the text field).
Suprisingly, when you hold a key, say in textarea, both KeyPress and KeyDown fire multiple times (Chrome 71), I'd use KeyDown if I need the event that fires multiple times and KeyUp for single key release.
KeyDown is usually better for games when you have to provide better responsiveness to their actions.
esc is usually processed via KeyDown: KeyPress doesn't fire and KeyUp behaves differently for inputs and textareas in different browsers (mostly due to loss of focus)
If you'd like to adjust height of a text area to the content, you probably won't use onKeyDown but rather onKeyPress (PS ok, it's actually better to use onChange for this case).
I've used all 3 in my project but unfortunately may have forgotten some of pragmatics. (to be noted: there's also input and change events)
onkeydown is fired when the key is down (like in shortcuts; for example, in Ctrl+A, Ctrl is held 'down'.
onkeyup is fired when the key is released (including modifier/etc keys)
onkeypress is fired as a combination of onkeydown and onkeyup, or depending on keyboard repeat (when onkeyup isn't fired). (this repeat behaviour is something that I haven't tested. If you do test, add a comment!)
textInput (webkit only) is fired when some text is entered (for example, Shift+A would enter uppercase 'A', but Ctrl+A would select text and not enter any text input. In that case, all other events are fired)
This article by Jan Wolter is the best piece I have came across, you can find the archived copy here if link is dead.
It explains all browser key events really well,
The keydown event occurs when the key is pressed, followed immediately by the keypress event. Then the keyup event is generated when the key is released.
To understand the difference between keydown and keypress, it is useful to distinguish between characters and keys. A key is a physical button on the computer's keyboard. A character is a symbol typed by pressing a button. On a US keyboard, hitting the 4 key while holding down the Shift key typically produces a "dollar sign" character. This is not necessarily the case on every keyboard in the world. In theory, the keydown and keyup events represent keys being pressed or released, while the keypress event represents a character being typed. In practice, this is not always the way it is implemented.
For a while, some browers fired an additional event, called textInput, immediately after keypress. Early versions of the DOM 3 standard intended this as a replacement for the keypress event, but the whole notion was later revoked. Webkit supported this between versions 525 and 533, and I'm told IE supported it, but I never detected that, possibly because Webkit required it to be called textInput while IE called it textinput.
There is also an event called input, supported by all browsers, which is fired just after a change is made to to a textarea or input field. Typically keypress will fire, then the typed character will appear in the text area, then input will fire. The input event doesn't actually give any information about what key was typed - you'd have to inspect the textbox to figure it out what changed - so we don't really consider it a key event and don't really document it here. Though it was originally defined only for textareas and input boxes, I believe there is some movement toward generalizing it to fire on other types of objects as well.
It seems that onkeypress and onkeydown do the same (whithin the small difference of shortcut keys already mentioned above).
You can try this:
<textarea type="text" onkeypress="this.value=this.value + 'onkeypress '"></textarea>
<textarea type="text" onkeydown="this.value=this.value + 'onkeydown '" ></textarea>
<textarea type="text" onkeyup="this.value=this.value + 'onkeyup '" ></textarea>
And you will see that the events onkeypress and onkeydown are both triggered while the key is pressed and not when the key is pressed.
The difference is that the event is triggered not once but many times (as long as you hold the key pressed). Be aware of that and handle them accordingly.
Updated Answer:
KeyDown
Fires multiple times when you hold keys down.
Fires meta key.
KeyPress
Fires multiple times when you hold keys down.
Does not fire meta keys.
KeyUp
Fires once at the end when you release key.
Fires meta key.
This is the behavior in both addEventListener and jQuery.
https://jsbin.com/vebaholamu/1/edit?js,console,output <-- try example
(answer has been edited with correct response, screenshot & example)
The onkeypress event works for all the keys except ALT, CTRL, SHIFT, ESC in all browsers where as onkeydown event works for all keys. Means onkeydown event captures all the keys.
Just wanted to share a curiosity:
when using the onkeydown event to activate a JS method, the charcode for that event is NOT the same as the one you get with onkeypress!
For instance the numpad keys will return the same charcodes as the number keys above the letter keys when using onkeypress, but NOT when using onkeydown !
Took me quite a few seconds to figure out why my script which checked for certain charcodes failed when using onkeydown!
Demo: https://www.w3schools.com/code/tryit.asp?filename=FMMBXKZLP1MK
and yes. I do know the definition of the methods are different.. but the thing that is very confusing is that in both methods the result of the event is retrieved using event.keyCode.. but they do not return the same value.. not a very declarative implementation.
Basically, these events act differently on different browser type and version, I created a little jsBin test and you can check the console for find out how these events behavior for your targeted environment, hope this help. http://jsbin.com/zipivadu/10/edit
The difference which I observed between keyup and keydown is
if we attach a eventhandler for keydown event and log the input box value i.e
(e.target.value) it returns whatever the value was before keydown event
But if we attach a eventhandler for keyup event and log the input box value
it returns the latest value including the key which was pressed
LETS UNDERSTAND WITH EXAMPLE
// the latest keypressed is not shown in e.target.value
// when keydown event handler is executed
// since until the keyup is not triggered
// the input box will not have that character in its value
const searchCitiesEleKeyDown = document.querySelector("#searchCities");
searchCitiesEleKeyDown.addEventListener("keydown", (e) => {
console.log(e.target.value);
});
// but in case of keyup event the e.target.value prints
// the text box content with the latest character pressed
// since as soon as the keyup event triggers
// the input box will have that character pressed in its value
const searchCitiesEleKeyUp = document.querySelector("#searchCities");
searchCitiesEleKeyUp.addEventListener("keyup", (e) => {
console.log(e.target.value);
});
<input type="text" id="searchCities" />
CodeSandbox Link
https://codesandbox.io/s/keydown-vs-keyup-wpj33m
A few practical facts that might be useful to decide which event to handle (run the script below and focus on the input box):
$('input').on('keyup keydown keypress',e=>console.log(e.type, e.keyCode, e.which, e.key))
<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<input/>
Pressing:
non inserting/typing keys (e.g. Shift, Ctrl) will not trigger a keypress. Press Ctrl and release it:
keydown 17 17 Control
keyup 17 17 Control
keys from keyboards that apply characters transformations to other characters may lead to Dead and duplicate "keys" (e.g. ~, ´) on keydown. Press ´ and release it in order to display a double ´´:
keydown 192 192 Dead
keydown 192 192 ´´
keypress 180 180 ´
keypress 180 180 ´
keyup 192 192 Dead
Additionally, non typing inputs (e.g. ranged <input type="range">) will still trigger all keyup, keydown and keypress events according to the pressed keys.
BLAZOR....
If you want to check which key is pressed use onkeypress OR onkeydown but if you want to get the text from the text field and then check the last key pressed for example you are scanning a barcode and you want to fire an even when the ENTER key is pressed (almost all barcode scanners send 13 "ENTER" in the last) then you should use onkeyup otherwise you will not get the text typed in the text field.
For example
<input type="text" class="form-control" #bind="#barcode" #onkeyup="BarCodeScan" placeholder="Scan" />
This will call the BarCodeScan function immediately after you will press enter by typing the code or if you scan it from scanner the BarCodeScan function will be called automatically. If you will use "onkeypress" or "onkeydown" here then the bind will not take place and you will not get the text from the text field.
Now I am developing a bar code based attendance system . Any there any javascript event can solve once the text field has detected the value has 10 characters, the text field will be fired and i can able to get the value.
Is there any solution ?
I'm not sure what you mean by "the text field will be fired", but you can find out when the 10th character is entered by binding to the keyup event:
document.getElementById("example").onkeyup = function() {
if(this.value.length === 10) {
console.log("ok");
}
};
It would be better to use addEventListener or attachEvent rather than setting the onkeyup property, but I'll leave that up to you.
Here's a working example.
you can check the length of the text input box value on every keypress and make a function call when its the 10th character.