Space Invaders

client.js

// client-side js
// run by the browser each time your view template is loaded
var player;
var playerSrc = "https://cdn.glitch.com/43e0016d-c8a0-4e4b-9451-241a4af8fb4f%2Fplayer.svg?1526019694966";
var invaderSrc = "https://cdn.glitch.com/43e0016d-c8a0-4e4b-9451-241a4af8fb4f%2Finvader.svg?1526019377700";

var dimension = 20; // base width and height for drawable objects
var canvasBound = 25;

var gameover = false;

(function(){
  
  class Main {
    constructor(){
      // get canvas & context
      this.canvas = document.getElementById("canvas");
      this.context = this.canvas.getContext('2d'); 

      // create player
      player = new Player(this);
      player.initialize();

      // create space invaders
      this.invaders = [];
      this.invaders = this.invaders.concat(createInvaders(this));
      
      // run timer
      this.timer();
    }
    
    // update() - update the positions of the player and invaders, to be drawn in draw()
    update(){
      player.update();
      
      // update invaders position
      for(var i = 0; i < this.invaders.length; i++){
        this.invaders[i].update();
      }
    }
    
    draw(canvas, context){
      context.clearRect(0, 0, canvas.width, canvas.height); // clear canvas
      // draw player
      context.drawImage(player.playerSVG, player.position.x, player.position.y, player.size.width, player.size.height);
      
      // draw invaders
      for(var i=0; i < this.invaders.length; i++){
        var invaderSVG = new Image();
        invaderSVG.src = invaderSrc;
        context.drawImage(invaderSVG, this.invaders[i].position.x, this.invaders[i].position.y, this.invaders[i].size.width, this.invaders[i].size.height);
      }
    }
    
    // timer() - update canvas for each animation frame
    timer(){
      this.update();
      this.draw(this.canvas, this.context);
      var self = this;
      
      var delayInMilliseconds = 0; // a delay to help with debugging
      setTimeout(function() {  
        if(!gameover){
          requestAnimationFrame(() => { self.timer() })
          // requestAnimationFrame(self.timer());  
        }else{
          // game over sequence
          self.context.clearRect(0, 0, self.canvas.width, self.canvas.height);
          self.context.textAlign = "center";
          self.context.fillText("GAME OVER!", self.canvas.width/2, self.canvas.height/2);
        }
      }, delayInMilliseconds);
    }
  }
  
  // Player that can be controlled using left and right arrow keys
  class Player{
    constructor(main){
      this.main = main;
      this.size = {width: dimension, height: dimension};
      this.position = {x: this.main.canvas.width/2-dimension/2, y: this.main.canvas.height-dimension};
    }
    
    initialize(){
      this.playerSVG = new Image();
      this.playerSVG.src = playerSrc;
      var self = this;
      this.playerSVG.onload = function(){
        // place player in middle of board to begin with
        self.main.context.drawImage(self.playerSVG, self.position.x, self.position.y, self.size.width, self.size.height);
      }
    }
    
    update(direction){
      if(direction == "left" && this.position.x > 0){
        this.position.x -= 5;
      }else if(direction == "right" && this.position.x < this.main.canvas.width-this.size.width){
        this.position.x += 5;
      }
    }
  }

  // listen for keyboard events to control player
 window.addEventListener('keydown', function(e){
    var left = 37; // keycode for left
    var right = 39; // keycode for right
    
    var key = e.keyCode ? e.keyCode : e.which;
    if(key == left){
      // console.log('left');
      player.update("left"); 
    }else if(key == right){
      // console.log('right');
      player.update("right");
    }
  });
  
  class Invader{
    constructor(main, position){
      this.main = main;
      this.size = {width: dimension, height: dimension};
      this.position = position;
      this.bounds = 0; // the bounds in which the invaders are still viewable in the convas
      this.xShift = 1; // amount the invader moves per timer increment
    }
    
    update(){
        if(this.bounds > canvasBound || this.bounds < -canvasBound){
        this.xShift = -this.xShift;
        this.position.y += 10;
        if(this.position.y > (this.main.canvas.height-player.size.height*2)){
          // touching the player - game is over!
          // console.log('game over!')
          gameover = true;          
        }
      }
      this.position.x += this.xShift;
      this.bounds += this.xShift;
    }
    
  }
  
  // createInvaders() creates an array of 24 invaders (6 columns, 4 rows)
  function createInvaders(main){
    var invadersArray = [];
    for(var i=0; i<24; i++){
      var x = canvasBound + (i % 8) * canvasBound;
      var y = canvasBound + (i % 3) * canvasBound;
      invadersArray.push(new Invader(main, {x: x, y: y}));
    }
    return invadersArray;
  }
  
  // runs application when the window has loaded
  window.addEventListener('load', function() {
    new Main();
  });
    
  
})()

index.html

<!DOCTYPE html>
<html lang="en">
  <head>
    <title>Tiff's Space Invader</title>
    <link id="favicon" rel="icon" href="https://glitch.com/edit/favicon-app.ico" type="image/x-icon">
    <meta charset="utf-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1">

    <!-- import the webpage's stylesheet -->
  </head>
  <body>    
    <canvas id="canvas" width="250px" height="250px"></canvas>
    
    
    <!-- import the webpage's client-side javascript file -->
    <script src="/client.js"></script>

  </body>
</html>

invader.svg

player.svg