smartgame/js/Level.js

import Player from './entities/Player';

export default class Level {
	constructor(canvas) {
		this.step = 1 / 120;

		this.canvas = canvas;
		this.ctx = canvas.getContext("2d");
		this.lastTime = null;
		this.raf = null;
		this.timeAcc = 0;
		this.entities = [];
	}

	spawn(ent, x, y) {
		ent.bounds.pos.set(x, y);
		this.entities.push(ent);
		ent.init();
	}

	physics(dt) {
		this.entities.forEach(ent =>
			ent.update(dt));
		this.entities.forEach(ent => {
			ent.bounds.pos.x += ent.velocity.x * dt;
			ent.bounds.pos.y += ent.velocity.y * dt;
		});
	}

	draw() {
		this.canvas.width = window.innerWidth;
		this.canvas.height = window.innerHeight;
		this.entities.forEach(ent => ent.draw(this.ctx));
	}

	update(time) {
		if (this.lastTime != null) {
			let dt = (time - this.lastTime) / 1000;

			this.timeAcc += dt;
			while (this.timeAcc > this.step) {
				this.physics(this.step);
				this.timeAcc -= this.step;
			}

			this.draw();
		}

		this.lastTime = time;
		this.raf = requestAnimationFrame(time => this.update(time));
	}

	start() {
		this.stop();
		this.lastTime = null;
		this.update();
	}

	stop() {
		if (this.raf != null) {
			cancelAnimationFrame(this.raf);
			this.raf = null;
		}
	}
}