Snowfall on Canvas with vanilla JavaScript.
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<html>
<head>
<style>
body {
margin: 0 auto;
}
#scene {
background-image: linear-gradient(#000fff, #888fff, #aaafff);
width: 100%;
height: 100vh;
}
</style>
</head>
<body>
<div id="scene"></div>
<script>
const canvas = document.createElement("canvas");
document.getElementById("scene").appendChild(canvas);
const context = canvas.getContext("2d");
function resize(){
canvas.setAttribute("width", innerWidth);
canvas.setAttribute("height", innerHeight);
context.fillStyle = "#fff";
context.shadowColor = "#fff";
}
resize();
addEventListener("resize", resize);
const flakes = [], interval = 4;
let last = 0, t = 0, index = 0;
function fall(){
requestAnimationFrame(fall);
if (++t - last > interval){
new Flake();
last = t;
}
context.clearRect(0, 0, innerWidth, innerHeight);
const removeList = []; // Removing flakes during the loop causes flickering...
for (let i = 0, l = flakes.length - 1; i < l; i++){
const flake = flakes[i];
if (flake.y > innerHeight){
removeList.push(flake);
}
else {
[flake.x, flake.y] = pointTranslate([flake.x, flake.y], flake.angle, flake.speed);
flake.draw();
}
}
// ...so we remove them in a separate loop.
for (let i = 0, l = removeList.length; i < l; i++){
removeList[i].remove();
}
}
fall();
function Flake(){
this.beenRemoved = false;
this.id = index++;
this.y = 0;
this.x = randBetween(0, innerWidth);
this.r = randBetween(2, 8);
this.angle = randBetween(80, 90);
this.speed = this.r / 2;
flakes.push(this);
this.remove = _ => {
if (!this.beenRemoved){
flakes.splice(flakes.indexOf(flakes.filter(f => f.id === this.id)[0]), 1);
this.beenRemoved = true;
}
}
this.draw = _ => {
context.shadowBlur = this.r / 2;
context.beginPath();
context.arc(this.x, this.y, this.r, 0, 2 * Math.PI);
context.fill();
context.shadowBlur = 2 + this.r / 2;
context.beginPath();
context.arc(this.x, this.y, this.r, 0, 2 * Math.PI);
context.fill();
}
return this;
}
function randBetween(min, max){
return Math.floor(Math.random() * (max - min + 1) + min);
}
function pointTranslate(point, angle, distance){
const r = angleToRadians(angle);
return [point[0] + distance * Math.cos(r), point[1] + distance * Math.sin(r)];
}
function angleToRadians(angle){
return angle / 180 * Math.PI;
}
</script>
</body>
</html>