Combining Bitmaps and Sound - HTML5 Canvas - page 465

than 0 . If a particle is available, it will be added to the particles array after its attributes
are set. If no particle is available, none will be used.
This functionality can be extended to add a particle as needed to the
pool when none is available. We have not added that functionality to
our example, but it is common in some pooling algorithms.
Here is the newly modified createExplode() function in its entirety:
function createExplode(x,y,num,type) {
playSound(SOUND_EXPLODE,.5);
for (var partCtr=0;partCtr<num;partCtr++){
if (particlePool.length > 0){
newParticle = particlePool.pop();
newParticle.dx = Math.random()*3;
if (Math.random()<.5){
newParticle.dx* = -1;
}
newParticle.dy = Math.random()*3;
if (Math.random()<.5){
newParticle.dy* = -1;
}
newParticle.life = Math.floor(Math.random()*30+30);
newParticle.lifeCtr = 0;
newParticle.x = x;
newParticle.width = 2;
newParticle.height = 2;
newParticle.y = y;
newParticle.type = type;
//ConsoleLog.log("newParticle.life=" + newParticle.life);
particles.push(newParticle);
}
}
}
The updateParticles() function will loop through the particles instances, update the
attributes of each, and then check to see whether the particle's life has been exhausted.
If it has, the function will place the particle back in the pool. Here is the code we will
add to updateParticles() to replenish the pool:
if (remove) {
particlePool.push(tempParticle)
particles.splice(particleCtr,1)
}