confetti.js

let canvas = document.getElementById('confetti');

var width = (window.innerWidth > 0) ? window.innerWidth : screen.width;
var Height = (window.innerHeight > 0) ? window.innerHeight : screen.height;

canvas.width = width;
canvas.height = Height;

let ctx = canvas.getContext('2d');
let pieces = [];
let numberOfPieces = 100;
let lastUpdateTime = Date.now();

function randomColor() {
    let colors = ['#f00', '#0f0', '#00f', '#0ff', '#f0f', '#ff0'];
    return colors[Math.floor(Math.random() * colors.length)];
}

function update() {
    let now = Date.now(),
        dt = now - lastUpdateTime;

    for (let i = pieces.length - 1; i >= 0; i--) {
        let p = pieces[i];

        if (p.y > canvas.height) {
            pieces.splice(i, 1);
            continue;
        }

        p.y += p.gravity * dt;
        p.rotation += p.rotationSpeed * dt;
    }


    while (pieces.length < numberOfPieces) {
        pieces.push(new Piece(Math.random() * canvas.width, -20));
    }

    lastUpdateTime = now;

    setTimeout(update, 1);
}

function draw() {
    ctx.clearRect(0, 0, canvas.width, canvas.height);

    pieces.forEach(function(p) {
        ctx.save();

        ctx.fillStyle = p.color;

        ctx.translate(p.x + p.size / 2, p.y + p.size / 2);
        ctx.rotate(p.rotation);

        ctx.fillRect(-p.size / 2, -p.size / 2, p.size, p.size);

        ctx.restore();
    });

    requestAnimationFrame(draw);
}

function Piece(x, y) {
    this.x = x;
    this.y = y;
    this.size = (Math.random() * 0.5 + 0.75) * 15;
    this.gravity = (Math.random() * 0.5 + 0.75) * 0.1;
    this.rotation = (Math.PI * 2) * Math.random();
    this.rotationSpeed = (Math.PI * 2) * (Math.random() - 0.5) * 0.001;
    this.color = randomColor();
}

while (pieces.length < numberOfPieces) {
    pieces.push(new Piece(Math.random() * canvas.width, Math.random() * canvas.height));
}

update();
draw();