JS Canvas Custom Webcam Pulse/Strobe Effect SRC

<center>
<body bgcolor="black">
<video id="video" autoplay hidden>
</video>
<canvas id="canvas" width="500" height="500"style="opacity:1.0">
<script>
var inn=prompt("Enter #:");
var video = document.getElementById("video");
var c = document.getElementById("canvas");
var ctx = c.getContext("2d");
var i=0;
var canvas = document.getElementById('canvas');
var context = canvas.getContext('2d');
var video = document.getElementById('video');
var mediaConfig = { video: true,audio:false};
navigator.mediaDevices.getUserMedia(mediaConfig).then(function(stream) {
video.src = this.window.URL.createObjectURL(stream);
video.play();
video.addEventListener("play", function() {i = window.setInterval(function() {
canvas.style.opacity-=0.1
if(canvas.style.opacity==0.0){
canvas.style.opacity++
}
ctx.drawImage(video,10,10,500,500)},inn);
}, false);
});
</script>