Canvas Games: Part I - HTML5 Canvas - page 679

update()

Is called from GAME_STATE_PLAY_LEVEL . It in turn calls the update() function for each
individual display object array.

Individual display object update() update() functions

The unique functions listed below update each different type of display object. These
functions(withtheexceptionof updatePlayer() )willloopthroughtherespectivear-
ray of objects associated with its type of display object and update the x and y values
with dx and dy values. The updateSaucer() function contains the logic necessary to
check whether to create a new saucer and whether any current saucers on the screen
should fire a missile at the player.

▪ updatePlayer()

▪ updatePlayerMissiles()

▪ updateRocks()

▪ updateSaucers()

▪ updateSaucerMissiles()

▪ updateParticles()

render()

Is called from GAME_STATE_PLAY_LEVEL . It in turn calls the render() function for each
individual display object array.

Individual display object render() render() functions

Like the update() functions, the unique functions listed below render each different
type of display object. Again, with the exception of the renderPlayer() object (be-
cause there is only a single player ship), each of these functions will loop through the
array of objects associated with its type and draw them to the game screen. As we saw
whendrawingtheplayershipearlierinthischapter,wewilldraweachobjectbymov-
ingandtranslatingthecanvastothepointatwhichwewanttodrawourlogicalobject.
Wewillthentransformourobject(ifnecessary)andpaintthepathstothegamescreen.

▪ renderPlayer()

▪ renderPlayerMissiles()