Working with Audio - HTML5 Canvas - page 601

In the canvasApp() function, we set up the following variables to use in the game.

The appState variable holds the current state variable:

var var appState = STATE_INIT ;

We use the loadCount and itemsToLoad variables in exactly the same way we used them in
the audio player application—except here we will be loading more items:

var var loadCount = 0 ;

var

var itemsToLoad = 0 ;

Thevariables alienImage , missileImage ,and playerImage willholdtheloadedimageswe
use in the game:

var var alienImage = new new Image ();

var var missileImage = new new Image ();

var var playerImage = new new Image ();

explodeSound and shootSound will hold the references to the HTMLAudioElement objects
we will load:

var var explodeSound ;

var var shootSound ;

The audioType variable will hold the extension of the valid audio file type for the browser
displaying the application:

var var audioType ;

The mouseX and mouseY variables will hold the current x and y location of the mouse:

var var mouseX ;

var

var mouseY ;

The player variable will hold a dynamic object with the x and y location of the player ship
(controlled with the mouse):

var var player = { x : 250 , y : 475 };

Both the aliens and missiles arrays will hold lists of dynamic objects for displaying aliens
and missiles on the canvas:

var var aliens = new new Array ();

var var missiles = new new Array ();

Thenextfivevariablessetthenumberofaliens( ALIEN_ROWS , ALIEN_COLS ),theirstartingloc-
ation ( ALIEN_START_X , ALIEN_START_Y ), and their spacing on screen ( ALIEN_SPACING ):