How do I detect when one of the arrow keys are pressed? I used this to find out:
function checkKey(e) {
var event = window.event ? window.event : e;
console.log(event.keyCode)
}
Though it worked for every other key, it didn't for arrow keys (maybe because the browser is supposed to scroll on these keys by default).
On key up and down call function. There are different codes for each key.
document.onkeydown = checkKey;
function checkKey(e) {
e = e || window.event;
if (e.keyCode == '38') {
// up arrow
}
else if (e.keyCode == '40') {
// down arrow
}
else if (e.keyCode == '37') {
// left arrow
}
else if (e.keyCode == '39') {
// right arrow
}
}
More recent and much cleaner: use event.key. No more arbitrary number codes! If you are transpiling or know your users are all on modern browsers, use this!
node.addEventListener('keydown', function(event) {
const key = event.key; // "ArrowRight", "ArrowLeft", "ArrowUp", or "ArrowDown"
});
Verbose Handling:
switch (event.key) {
case "ArrowLeft":
// Left pressed
break;
case "ArrowRight":
// Right pressed
break;
case "ArrowUp":
// Up pressed
break;
case "ArrowDown":
// Down pressed
break;
}
Modern Switch Handling:
const callback = {
"ArrowLeft" : leftHandler,
"ArrowRight" : rightHandler,
"ArrowUp" : upHandler,
"ArrowDown" : downHandler,
}[event.key]
callback?.()
NOTE: The old properties (
.keyCodeand.which) are Deprecated.
"w", "a", "s", "d" for direction, use event.codeTo support users who are using non-qwerty/English keyboard layouts, you should instead use event.code. This will preserve physical key location, even if resulting character changes.
event.key would be , on Dvorak and z on Azerty, making your game unplayable.
const {code} = event
if (code === "KeyW") // KeyA, KeyS, KeyD
Optimally, you also allow key remapping, which benefits the player regardless of their situation.
P.S. event.code is the same for arrows
Possibly the tersest formulation:
document.onkeydown = function(e) {
switch (e.keyCode) {
case 37:
alert('left');
break;
case 38:
alert('up');
break;
case 39:
alert('right');
break;
case 40:
alert('down');
break;
}
};
Demo (thanks to user Angus Grant): http://jsfiddle.net/angusgrant/E3tE6/
This should work cross-browser. Leave a comment if there is a browser where it does not work.
There are other ways to get the key code (e.which, e.charCode, and window.event instead of e), but they should not be necessary. You can try most of them out at http://www.asquare.net/javascript/tests/KeyCode.html. Note that event.keycode does not work with onkeypress in Firefox, but it does work with onkeydown.
Use keydown, not keypress for non-printable keys such as arrow keys:
function checkKey(e) {
e = e || window.event;
alert(e.keyCode);
}
document.onkeydown = checkKey;
The best JavaScript key event reference I've found (beating the pants off quirksmode, for example) is here: http://unixpapa.com/js/key.html
I believe the most recent method would be:
document.addEventListener("keydown", function(event) {
event.preventDefault();
const key = event.key; // "ArrowRight", "ArrowLeft", "ArrowUp", or "ArrowDown"
switch (key) { // change to event.key to key to use the above variable
case "ArrowLeft":
// Left pressed
<do something>
break;
case "ArrowRight":
// Right pressed
<do something>
break;
case "ArrowUp":
// Up pressed
<do something>
break;
case "ArrowDown":
// Down pressed
<do something>
break;
}
});
This assumes the developer wants the code to be active anywhere on the page and the client should ignore any other key presses. Eliminate the event.preventDefault(); line if keypresses, including those caught by this handler should still be active.
Here's an example implementation:
var targetElement = $0 || document.body;
function getArrowKeyDirection (keyCode) {
return {
37: 'left',
39: 'right',
38: 'up',
40: 'down'
}[keyCode];
}
function isArrowKey (keyCode) {
return !!getArrowKeyDirection(keyCode);
}
targetElement.addEventListener('keydown', function (event) {
var direction,
keyCode = event.keyCode;
if (isArrowKey(keyCode)) {
direction = getArrowKeyDirection(keyCode);
console.log(direction);
}
});
Here's how I did it:
var leftKey = 37, upKey = 38, rightKey = 39, downKey = 40;
var keystate;
document.addEventListener("keydown", function (e) {
keystate[e.keyCode] = true;
});
document.addEventListener("keyup", function (e) {
delete keystate[e.keyCode];
});
if (keystate[leftKey]) {
//code to be executed when left arrow key is pushed.
}
if (keystate[upKey]) {
//code to be executed when up arrow key is pushed.
}
if (keystate[rightKey]) {
//code to be executed when right arrow key is pushed.
}
if (keystate[downKey]) {
//code to be executed when down arrow key is pushed.
}
I've been able to trap them with jQuery:
$(document).keypress(function (eventObject) {
alert(eventObject.keyCode);
});
An example: http://jsfiddle.net/AjKjU/
That is the working code for chrome and firefox
<html>
<head>
<script type="text/javascript" src="http://ajax.googleapis.com/ajax/libs/jquery/1.4.1/jquery.min.js"></script>
<script type="text/javascript">
function leftArrowPressed() {
alert("leftArrowPressed" );
window.location = prevUrl
}
function rightArrowPressed() {
alert("rightArrowPressed" );
window.location = nextUrl
}
function topArrowPressed() {
alert("topArrowPressed" );
window.location = prevUrl
}
function downArrowPressed() {
alert("downArrowPressed" );
window.location = nextUrl
}
document.onkeydown = function(evt) {
var nextPage = $("#next_page_link")
var prevPage = $("#previous_page_link")
nextUrl = nextPage.attr("href")
prevUrl = prevPage.attr("href")
evt = evt || window.event;
switch (evt.keyCode) {
case 37:
leftArrowPressed(nextUrl);
break;
case 38:
topArrowPressed(nextUrl);
break;
case 39:
rightArrowPressed(prevUrl);
break;
case 40:
downArrowPressed(prevUrl);
break;
}
};
</script>
</head>
<body>
<p>
<a id="previous_page_link" href="http://www.latest-tutorial.com">Latest Tutorials</a>
<a id="next_page_link" href="http://www.zeeshanakhter.com">Zeeshan Akhter</a>
</p>
</body>
</html>
I was also looking for this answer until I came across this post.
I've found another solution to know the keycode of the different keys, courtesy to my problem. I just wanted to share my solution.
Just use keyup/keydown event to write the value in the console/alert the same using event.keyCode. like-
console.log(event.keyCode)
// or
alert(event.keyCode)
- rupam
This library rocks! https://craig.is/killing/mice
Mousetrap.bind('up up down down left right left right b a enter', function() {
highlight([21, 22, 23]);
});
You need to press the sequence a bit fast to highlight the code in that page though.
Re answers that you need keydown not keypress.
Assuming you want to move something continuously while the key is pressed, I find that keydown works for all browsers except Opera. For Opera, keydown only triggers on 1st press. To accommodate Opera use:
document.onkeydown = checkKey;
document.onkeypress = checkKey;
function checkKey(e)
{ etc etc
Arrow Keys are triggered on keyup
$(document).on("keyup", "body", function(e) {
if (e.keyCode == 38) {
// up arrow
console.log("up arrow")
}
if (e.keyCode == 40) {
// down arrow
console.log("down arrow")
}
if (e.keyCode == 37) {
// left arrow
console.log("lefy arrow")
}
if (e.keyCode == 39) {
// right arrow
console.log("right arrow")
}
})
onkeydown allows ctrl, alt, shits
onkeyup allows tab, up arrows, down arrows, left arrows, down arrows
If you use jquery then you can also do like this,
$(document).on("keydown", '.class_name', function (event) {
if (event.keyCode == 37) {
console.log('left arrow pressed');
}
if (event.keyCode == 38) {
console.log('up arrow pressed');
}
if (event.keyCode == 39) {
console.log('right arrow pressed');
}
if (event.keyCode == 40) {
console.log('down arrow pressed');
}
});
With key and ES6.
This gives you a separate function for each arrow key without using switch and also works with the 2,4,6,8 keys in the numpad when NumLock is on.
const element = document.querySelector("textarea"),
ArrowRight = k => {
console.log(k);
},
ArrowLeft = k => {
console.log(k);
},
ArrowUp = k => {
console.log(k);
},
ArrowDown = k => {
console.log(k);
},
handler = {
ArrowRight,
ArrowLeft,
ArrowUp,
ArrowDown
};
element.addEventListener("keydown", e => {
const k = e.key;
if (handler.hasOwnProperty(k)) {
handler[k](k);
}
});<p>Click the textarea then try the arrows</p>
<textarea></textarea>