<> Where do you mean HTML5+JS Fireworks effect

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<!DOCTYPE html> <html dir="ltr" lang="zh-CN"> <head> <meta charset="UTF-8" /> <
meta name="viewport" content="width=device-width" /> <title> With interactive function HTML5+JS Fireworks effect </
title> <style> /* basic styles for black background and crosshair cursor */ body
{ background: #000; margin: 0; } canvas { cursor: crosshair; display: block; }
</style> </head> <canvas id="canvas">Canvas is not supported in your browser.</
canvas> <script> // 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'; // 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 fireworks.push( new Firework( cw / 2, ch
, random( 0, cw ), random( 0, ch / 2 ) ) ); 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, 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; </script>

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