Capturing User Input - Beginning HTML5 Games with CreateJS - page 41

Listing 3-11. Controlling a Game Paddle Using Arrow Keys
const ARROW_KEY_LEFT = 37;
const ARROW_KEY_RIGHT = 39;
var stage,padel;
var leftKeyDown,rightKeyDown = false;
function init() {
stage = new createjs.Stage(document.getElementById('canvas'));
createjs.Ticker.addEventListener("tick", tick);
createjs.Ticker.setFPS(60);
startGame();
}
function startGame() {
padel = new createjs.Shape();
padel.width = 100;
padel.graphics.beginFill('#0000FF').drawRect(0, 0, padel.width, 20);
padel.x = padel.nextX = 0;
padel.y = stage.canvas.height - 20;
stage.addChild(padel);
//handle keys
window.onkeydown = movePadel;
window.onkeyup = stopPadel;
}
function movePadel(e) {
e = !e ? window.event : e;
switch (e.keyCode) {
case ARROW_KEY_LEFT:
leftKeyDown = true;
break;
case ARROW_KEY_RIGHT:
rightKeyDown = true;
break;
}
}
function stopPadel(e) {
e = !e ? window.event : e;
switch (e.keyCode) {
case 37:
leftKeyDown = false;
break;
case 39:
rightKeyDown = false;
break;
}
}