Simple library for JavaScript key code constants and key press state


Simple library for JavaScript key code constants and a utility to check key press state. It is a port of my KeyAS3 library.

Many existing libraries expose key code values in strange ways (such as requiring function calls that took string values). This library provides a simple static object containing the key codes, and comes with an additional utility function for checking the pressed state of keys. The API is heavily influenced by the Key class from the olden days of ActionScript 2.0.



var KeyJS = require('key-js');

<script> Tag

When loaded through a <script> tag in the browser, KeyJS will become a global variable on the window object.

Retrieving Key Code Constants

The KeyJS object exposes the key code values as values attached to the object itself. See below:

console.log(KeyJS.A); // 65
console.log(KeyJS.ENTER); // 13
console.log(KeyJS.SPACEBAR); // 32

See key.js for a full list of all the constants

Checking the state of the Keyboard

By default KeyJS will not listen for Keyboard events. You can use the function KeyJS.startCapture() to start the listeners. The full API can then be accessed as outlined below:

KeyJS.startCapture(target = null) - Starts listening for keyboard events on the target DOM element. By default this will be set to the window object. Note that keyboard events are only tracked while the target has focus. This means you don't have to worry about key presses becoming "stuck" in the pressed state when focus is lost.

KeyJS.endCapture() - Stops listening for keyboard events.

KeyJS.isDown(keyCode) - Checks the "pressed" state of the specified key specified by its key code.

Example Code

var KeyJS = require('key-js');

setInterval(function () {
  // Check console to see when spacebar is pressed
  console.log('Spacebar pressed: ' + KeyJS.isDown(KeyJS.SPACEBAR));
}, 100);





欢迎 JavaScript 爱好者