040 : Node 040

// Global variables. var _game = {}; var _player = {}; function setup() { window.addEventListener("load", handle_load, false); window.addEventListener("keydown", handle_keydown, false); window.addEventListener("keyup", handle_keyup, false); } // Handle the load event (which is sent when the page has finished loading). function handle_load(event) { init(); requestAnimationFrame(update_world); } function handle_keydown(event) { _game.keymap[event.keyCode] = true; } function handle_keyup(event) { _game.keymap[event.keyCode] = false; } // Initialize the game state. function init() { init_game(); init_player(); } // Initialize general game state info. function init_game() { var canvas = document.getElementById("stage"); canvas.width = 550; canvas.height = 400; _game.width = canvas.width; _game.height = canvas.height; // The keymap keeps track of which keys are currently being pressed. _game.keymap = {}; } // Initialize player data. function init_player() { _player.x = 0; _player.y = 0; _player.width = 20; _player.height = 20; _player.velocity_x = 0; _player.velocity_y = 0; } // Erase the canvas and draw all the objects. function draw() { var canvas = document.getElementById("stage"); var ctx = canvas.getContext("2d"); erase(ctx); draw_player(ctx); } // Erase the canvas by filling it with white. function erase(ctx) { ctx.fillStyle = "#ffffff"; ctx.fillRect(0, 0, _game.width, _game.height); } // Draw the player. function draw_player(ctx) { ctx.fillStyle = "blue"; ctx.fillRect(_player.x, _player.y, _player.width, _player.height); } // Handle input and move the player. function update_player() { check_input(); // Move the player to the new location. _player.x += _player.velocity_x; _player.y += _player.velocity_y; } function check_input() { _player.velocity_x = 0; _player.velocity_y = 0; // Left arrow or 'a' to move left. if (_game.keymap[37] || _game.keymap[65]) { _player.velocity_x = -1; } // Right arrow or 'd' to move right. if (_game.keymap[39] || _game.keymap[68]) { _player.velocity_x = 1; } // Up arrow or 'w' to move up. if (_game.keymap[38] || _game.keymap[87]) { _player.velocity_y = -1; } // Down arrow or 's' to move up. if (_game.keymap[40] || _game.keymap[83]) { _player.velocity_y = 1; } } // This is called ~60 times per second to update the world. function update_world() { update_player(); draw(); requestAnimationFrame(update_world); } setup();