Detecting arrow key presses in JavaScript

Question

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).

Answer 1

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.

Answer 2

event.key === "ArrowRight"...

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;
}

You can easily extend this to check for "w", "a", "s", "d", or any other key

Mozilla Docs

Supported Browsers

P.S. event.code is the same for arrows

Answer 3

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);
  }
});

Answer 4

arrow keys are only triggered by onkeydown, not onkeypress

keycodes are:

• left = 37
• up = 38
• right = 39
• down = 40

Answer 5

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

Answer 6

Modern answer since keyCode is now deprecated in favor of key:

document.onkeydown = function (e) {
    switch (e.key) {
        case 'ArrowUp':
            // up arrow
            break;
        case 'ArrowDown':
            // down arrow
            break;
        case 'ArrowLeft':
            // left arrow
            break;
        case 'ArrowRight':
            // right arrow
    }
};