Here is a hello world simple skeleton I wrote to get started on an HTML5/javascript game. I converted it from a python example provided in Coursera's An Introduction to Interactive Programming in Python which demonstrates how to start moving a ball around a canvas using arrow keys.I did this as a learning exercise to get to grips with javascript. While I've got this code to pass jslint, I was wondering if more experienced javascript coders could suggest better ways of doing this.var canvas, context, ball_pos, vel, keys = {};var BALL_RADIUS = 20;function init() {    'use strict';    canvas = document.getElementById('c');    context = canvas.getContext('2d');    ball_pos = [canvas.width / 2, canvas.height / 2];    vel = 4;}function draw() {    'use strict';    // draw background    context.fillStyle = 'black';    context.fillRect(0, 0, canvas.width, canvas.height);    // draw ball    context.strokeStyle = 'red';    context.lineWidth = 2;    context.fillStyle = 'white';    context.beginPath();    context.arc(ball_pos[0], ball_pos[1], BALL_RADIUS, 0, Math.PI * 2, true);    context.closePath();    context.fill();    context.stroke();}function keydown(evt) {    'use strict';    // mozilla based browsers return which and others keyCode    var keyCode = evt.which || evt.keyCode;    keys[keyCode] = true;    // alert(keyCode)    // 33 up right    // 34 down right    // 35 down right    // 36 up left    if (keys[37]) { // left        ball_pos[0] -= vel;    }    if (keys[38]) { // up        ball_pos[1] -= vel;    }    if (keys[39]) { // right        ball_pos[0] += vel;    }    if (keys[40]) { // down        ball_pos[1] += vel;    }}function keyup(evt) {    'use strict';    var keyCode = evt.which || evt.keyCode;    delete keys[keyCode];}function animate() {    'use strict';    window.requestAnimationFrame(animate);    draw();}// register event handlerswindow.onkeydown = keydown;window.onkeyup = keyup;init();animate();<!DOCTYPE HTML><html><head>  <meta charset=utf-8></head><body>  <canvas id=c width=600 height=400></canvas></body></html>
Simple example to get started with a browser based game
javascript;game;html5