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// when animating on canvas, it is best to use requestAnimationFrame instead of setTimeout or setInterval
// not supported in all browsers though and sometimes needs a prefix, so we need a shim
window.requestAnimFrame = (function () {
    return window.requestAnimationFrame ||
        window.webkitRequestAnimationFrame ||
        window.mozRequestAnimationFrame ||
        function (callback) {
            window.setTimeout(callback, 1000 / 60);
        };
})();

// now we will setup our basic variables for the demo
var canvas = document.getElementById('canvas'),
    ctx = canvas.getContext('2d'),
    // full screen dimensions
    cw = window.innerWidth,
    ch = window.innerHeight,
    // firework collection
    fireworks = [],
    // particle collection
    particles = [],
    // starting hue
    hue = 120,
    // when launching fireworks with a click, too many get launched at once without a limiter, one launch per 5 loop ticks
    limiterTotal = 5,
    limiterTick = 0,
    // this will time the auto launches of fireworks, one launch per 80 loop ticks
    timerTotal = 80,
    timerTick = 0,
    mousedown = false,
    // mouse x coordinate,
    mx,
    // mouse y coordinate
    my;

// set canvas dimensions
canvas.width = cw;
canvas.height = ch;

// now we are going to setup our function placeholders for the entire demo

// get a random number within a range
function random(min, max) {
    return Math.random() * (max - min) + min;
}

// calculate the distance between two points
function calculateDistance(p1x, p1y, p2x, p2y) {
    var xDistance = p1x - p2x,
        yDistance = p1y - p2y;
    return Math.sqrt(Math.pow(xDistance, 2) + Math.pow(yDistance, 2));
}

// create firework
function Firework(sx, sy, tx, ty) {
    // actual coordinates
    this.x = sx;
    this.y = sy;
    // starting coordinates
    this.sx = sx;
    this.sy = sy;
    // target coordinates
    this.tx = tx;
    this.ty = ty;
    // distance from starting point to target
    this.distanceToTarget = calculateDistance(sx, sy, tx, ty);
    this.distanceTraveled = 0;
    // track the past coordinates of each firework to create a trail effect, increase the coordinate count to create more prominent trails
    this.coordinates = [];
    this.coordinateCount = 3;
    // populate initial coordinate collection with the current coordinates
    while (this.coordinateCount--) {
        this.coordinates.push([this.x, this.y]);
    }
    this.angle = Math.atan2(ty - sy, tx - sx);
    this.speed = 2;
    this.acceleration = 1.05;
    this.brightness = random(50, 70);
    // circle target indicator radius
    this.targetRadius = 1;
}

// update firework
Firework.prototype.update = function (index) {
    // remove last item in coordinates array
    this.coordinates.pop();
    // add current coordinates to the start of the array
    this.coordinates.unshift([this.x, this.y]);

    // cycle the circle target indicator radius
    if (this.targetRadius < 8) {
        this.targetRadius += 0.3;
    } else {
        this.targetRadius = 1;
    }

    // speed up the firework
    this.speed *= this.acceleration;

    // get the current velocities based on angle and speed
    var vx = Math.cos(this.angle) * this.speed,
        vy = Math.sin(this.angle) * this.speed;
    // how far will the firework have traveled with velocities applied?
    this.distanceTraveled = calculateDistance(this.sx, this.sy, this.x + vx, this.y + vy);

    // if the distance traveled, including velocities, is greater than the initial distance to the target, then the target has been reached
    if (this.distanceTraveled >= this.distanceToTarget) {
        createParticles(this.tx, this.ty);
        // remove the firework, use the index passed into the update function to determine which to remove
        fireworks.splice(index, 1);
    } else {
        // target not reached, keep traveling
        this.x += vx;
        this.y += vy;
    }
}

// draw firework
Firework.prototype.draw = function () {
    ctx.beginPath();
    // move to the last tracked coordinate in the set, then draw a line to the current x and y
    ctx.moveTo(this.coordinates[this.coordinates.length - 1][0], this.coordinates[this.coordinates.length - 1][
        1
    ]);
    ctx.lineTo(this.x, this.y);
    ctx.strokeStyle = 'hsl(' + hue + ', 100%, ' + this.brightness + '%)';
    ctx.stroke();

    ctx.beginPath();
    // draw the target for this firework with a pulsing circle
    ctx.arc(this.tx, this.ty, this.targetRadius, 0, Math.PI * 2);
    ctx.stroke();
}

// create particle
function Particle(x, y) {
    this.x = x;
    this.y = y;
    // track the past coordinates of each particle to create a trail effect, increase the coordinate count to create more prominent trails
    this.coordinates = [];
    this.coordinateCount = 5;
    while (this.coordinateCount--) {
        this.coordinates.push([this.x, this.y]);
    }
    // set a random angle in all possible directions, in radians
    this.angle = random(0, Math.PI * 2);
    this.speed = random(1, 10);
    // friction will slow the particle down
    this.friction = 0.95;
    // gravity will be applied and pull the particle down
    this.gravity = 1;
    // set the hue to a random number +-20 of the overall hue variable
    this.hue = random(hue - 20, hue + 20);
    this.brightness = random(50, 80);
    this.alpha = 1;
    // set how fast the particle fades out
    this.decay = random(0.015, 0.03);
}

// update particle
Particle.prototype.update = function (index) {
    // remove last item in coordinates array
    this.coordinates.pop();
    // add current coordinates to the start of the array
    this.coordinates.unshift([this.x, this.y]);
    // slow down the particle
    this.speed *= this.friction;
    // apply velocity
    this.x += Math.cos(this.angle) * this.speed;
    this.y += Math.sin(this.angle) * this.speed + this.gravity;
    // fade out the particle
    this.alpha -= this.decay;

    // remove the particle once the alpha is low enough, based on the passed in index
    if (this.alpha <= this.decay) {
        particles.splice(index, 1);
    }
}



// draw particle
Particle.prototype.draw = function () {

    ctx.beginPath();
    // move to the last tracked coordinates in the set, then draw a line to the current x and y
    ctx.moveTo(this.coordinates[this.coordinates.length - 1][0], this.coordinates[this.coordinates.length - 1][
        1
    ]);
    ctx.lineTo(this.x, this.y);
    ctx.strokeStyle = 'hsla(' + this.hue + ', 100%, ' + this.brightness + '%, ' + this.alpha + ')';
    ctx.stroke();

}

// create particle group/explosion
function createParticles(x, y) {
    // increase the particle count for a bigger explosion, beware of the canvas performance hit with the increased particles though
    var particleCount = 30;
    while (particleCount--) {
        particles.push(new Particle(x, y));
    }
}

// main demo loop
function loop() {
    // this function will run endlessly with requestAnimationFrame
    requestAnimFrame(loop);

    // increase the hue to get different colored fireworks over time
    hue += 0.5;

    // normally, clearRect() would be used to clear the canvas
    // we want to create a trailing effect though
    // setting the composite operation to destination-out will allow us to clear the canvas at a specific opacity, rather than wiping it entirely
    ctx.globalCompositeOperation = 'destination-out';
    // decrease the alpha property to create more prominent trails
    ctx.fillStyle = 'rgba(0, 0, 0, 0.5)';
    ctx.fillRect(0, 0, cw, ch);
    // change the composite operation back to our main mode
    // lighter creates bright highlight points as the fireworks and particles overlap each other
    ctx.globalCompositeOperation = 'lighter';

    var text = "HAPPY NEW YEAR !";
    ctx.font = "50px sans-serif";
    var textData = ctx.measureText(text);
    ctx.fillStyle = "rgba(" + parseInt(random(0, 255)) + "," + parseInt(random(0, 255)) + "," + parseInt(random(0,
        255)) + ",0.3)";
    ctx.fillText(text, cw / 2 - textData.width / 2, ch / 2);

    // loop over each firework, draw it, update it
    var i = fireworks.length;
    while (i--) {
        fireworks[i].draw();
        fireworks[i].update(i);
    }

    // loop over each particle, draw it, update it
    var i = particles.length;
    while (i--) {
        particles[i].draw();
        particles[i].update(i);
    }

    // launch fireworks automatically to random coordinates, when the mouse isn't down
    if (timerTick >= timerTotal) {
        if (!mousedown) {
            // start the firework at the bottom middle of the screen, then set the random target coordinates, the random y coordinates will be set within the range of the top half of the screen

            for (var h = 0; h < 50; h++) {
                fireworks.push(new Firework(cw / 2, ch / 2, random(0, cw), random(0, ch)));
            }

            timerTick = 0;
        }
    } else {
        timerTick++;
    }

    // limit the rate at which fireworks get launched when mouse is down
    if (limiterTick >= limiterTotal) {
        if (mousedown) {
            // start the firework at the bottom middle of the screen, then set the current mouse coordinates as the target
            fireworks.push(new Firework(cw / 2, ch / 2, mx, my));
            limiterTick = 0;
        }
    } else {
        limiterTick++;
    }
}

// mouse event bindings
// update the mouse coordinates on mousemove
canvas.addEventListener('mousemove', function (e) {
    mx = e.pageX - canvas.offsetLeft;
    my = e.pageY - canvas.offsetTop;
});

// toggle mousedown state and prevent canvas from being selected
canvas.addEventListener('mousedown', function (e) {
    e.preventDefault();
    mousedown = true;
});

canvas.addEventListener('mouseup', function (e) {
    e.preventDefault();
    mousedown = false;
});

// once the window loads, we are ready for some fireworks!
window.onload = loop;
<canvas id="canvas"></canvas>
body {
    background: #000;
    margin: 0;
}

canvas {
    cursor: crosshair;
    display: block;
}