Here's my original createParticle() function, showing the wasteful creation of objects every time a particle is created

createParticle.js

function createParticle(
    definitionName,
    position,
    velocity) {
    var definition = descriptors[definitionName];
    if (definition === undefined) {
        return undefined;
    }

    var particle = {
        position: position,
        previousPosition: {
            x: position.x,
            y: position.y
        },
        velocity: velocity,
        frameIndex: 0,
        isWithinGameBounds: true,
        frames: definition.frameParams,
        isDestroyed: false,
        isLive: isLive,
        wrap: definition.wrap || false,
        move: move
    };

    particles.push(particle);

    return particle;

    function isLive() {
        return (particle.isWithinGameBounds || particle.wrap)
            && !particle.isDestroyed
            && particle.frameIndex < particle.frames.length;
    }

    function move() {
        if (!isLive()) {
            return;
        }
        particle.previousPosition.x = particle.position.x;
        particle.previousPosition.y = particle.position.y;
        particle.position.x += particle.velocity.x;
        particle.position.y += particle.velocity.y;
        particle.frameIndex++;

        if (particle.wrap) {
            wrapper.wrap(particle);
        }
        else if (!gameDimensions.isWithinGameBounds(particle.position)) {
            particle.isWithinGameBounds = false;
        }
    }
}