How to Handle Arrow Key Events in JavaScript/jQuery?

Handling Arrow Key Events in Javascript/jQuery

When working with keyboard input in Javascript or jQuery, binding functions to specific keys can be crucial for controlling user interactions and providing responsive navigation. In this context, a common challenge is capturing left and right arrow key events. Contrary to popular belief, the js-hotkey plugin for jQuery does not natively support arrow key binding.

Using Plain Javascript

For straightforward binding without the use of external libraries, consider the following code snippet:

<code class="javascript">document.onkeydown = function(e) {
    switch(e.which) {
        case 37: // left
        break;

        case 38: // up
        break;

        case 39: // right
        break;

        case 40: // down
        break;

        default: return; // exit this handler for other keys
    }
    e.preventDefault(); // prevent the default action (scroll / move caret)
};</code>

In this code, key events are monitored using the onkeydown event handler. Arrow keys are identified by their respective which values (e.g., 37 for left, 39 for right). To prevent default browser behaviors such as scrolling or caret movement, the preventDefault() method is employed.

Supporting IE8

If you need to support Internet Explorer 8, which does not support the which property, you can augment the code as follows:

<code class="javascript">document.onkeydown = function(e) {
    e = e || window.event; // IE8 compatibility
    switch(e.which || e.keyCode) {
        // ...
    }
};</code>

Modern Solution: KeyboardEvent.key

In modern browsers, the KeyboardEvent.which property has been deprecated. For a more up-to-date approach to detecting arrow keys, you can utilize the KeyboardEvent.key property instead:

<code class="javascript">document.addEventListener('keydown', (event) => {
  switch (event.key) {
    case 'ArrowLeft': // left
      break;
    case 'ArrowUp': // up
      break;
    case 'ArrowRight': // right
      break;
    case 'ArrowDown': // down
      break;
    default: return;
  }
});</code>

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