guest_worker/scanimation/interfaces/animation/script.js

let cnv = document.getElementById('cnv'),
		ctx = cnv.getContext('2d')


let frames_folder = '../frames/',
    imgs = [],
    new_imgs = []


let add_img = (new_img) => {
  let img = new Image()
      img.src = `${frames_folder}${new_img}`
      img.onload = function(){
          console.log(`loaded ${new_img}`)
      }
      imgs.push(img)
}



// SOCKET //////////////////////////////////////////////////////////////////////

				let socket = io.connect('/')

				socket.on('connection', function(){
				  console.log('connected to node server')
					socket.emit('animationInit')
          makeAnimation()
				})

				socket.on('frameData', function(data){
					imgs.length < data.frames.length ? new_imgs = data.frames.slice(imgs.length) : new_imgs = []
          new_imgs.forEach(function(img){ add_img(img) })
				})




// ANIMATION ///////////////////////////////////////////////////////////////////

				let frames_per_sec = 7,
				    current_frame = 0,
						forward = true

				function makeAnimation(){
				    let now,
				        delta = 0,
				        last = timeStamp(),
				        step = 1/frames_per_sec

				    function frame() {
				      now = timeStamp()
				      delta += Math.min(1, (now - last) / 1000)
				      while(delta > step){
				        delta -= step
				        update(step)
				      }
				      last = now
				      requestAnimationFrame(frame)
				    }
				    requestAnimationFrame(frame)
				}

				function update(step){
					if (imgs.length < 1) return;
					if (current_frame == (imgs.length-1)) forward = false
					else if (current_frame == 0) forward = true
					forward ? current_frame++ : current_frame--

					ctx.drawImage(imgs[current_frame], 0, 0)
					// console.log(current_frame)
				}


        function timeStamp(){ return window.performance && window.performance.now ? window.performance.now() : new Date().getTime() }