这段JS代码的功能是实现烟花爆炸后的小颗粒的绘制，从draw方法中可以看出，创建几个随机点，烟花颗粒即可在这个范围的随机点中散落。

var Firework = function(startX, startY, targetX, targetY){ this.x = startX; this.y = startY; this.startX = startX; this.startY = startY; this.hitX = false; this.hitY = false; this.coordLast = [ {x: startX, y: startY}, {x: startX, y: startY}, {x: startX, y: startY} ]; this.targetX = targetX; this.targetY = targetY; this.speed = self.fworkSpeed; this.angle = Math.atan2(targetY - startY, targetX - startX); this.shockwaveAngle = Math.atan2(targetY - startY, targetX - startX)+(90*(Math.PI/180)); this.acceleration = self.fworkAccel/100; this.hue = self.currentHue; this.brightness = rand(50, 80); this.alpha = rand(50,100)/100; this.lineWidth = self.lineWidth; this.targetRadius = 1; }; Firework.prototype.update = function(index){ self.ctx.lineWidth = this.lineWidth; vx = Math.cos(this.angle) * this.speed, vy = Math.sin(this.angle) * this.speed; this.speed *= 1 + this.acceleration; this.coordLast[2].x = this.coordLast[1].x; this.coordLast[2].y = this.coordLast[1].y; this.coordLast[1].x = this.coordLast[0].x; this.coordLast[1].y = this.coordLast[0].y; this.coordLast[0].x = this.x; this.coordLast[0].y = this.y; if(self.showTarget){ if(this.targetRadius < 8){ this.targetRadius += .25 * self.dt; } else { this.targetRadius = 1 * self.dt; } } if(this.startX >= this.targetX){ if(this.x + vx <= this.targetX){ this.x = this.targetX; this.hitX = true; } else { this.x += vx * self.dt; } } else { if(this.x + vx >= this.targetX){ this.x = this.targetX; this.hitX = true; } else { this.x += vx * self.dt; } } if(this.startY >= this.targetY){ if(this.y + vy <= this.targetY){ this.y = this.targetY; this.hitY = true; } else { this.y += vy * self.dt; } } else { if(this.y + vy >= this.targetY){ this.y = this.targetY; this.hitY = true; } else { this.y += vy * self.dt; } } if(this.hitX && this.hitY){ var randExplosion = rand(0, 9); self.createParticles(this.targetX, this.targetY, this.hue); self.fireworks.splice(index, 1); } }; Firework.prototype.draw = function(){ self.ctx.lineWidth = this.lineWidth; var coordRand = (rand(1,3)-1); self.ctx.beginPath(); self.ctx.moveTo(Math.round(this.coordLast[coordRand].x), Math.round(this.coordLast[coordRand].y)); self.ctx.lineTo(Math.round(this.x), Math.round(this.y)); self.ctx.closePath(); self.ctx.strokeStyle = 'hsla('+this.hue+', 100%, '+this.brightness+'%, '+this.alpha+')'; self.ctx.stroke(); if(self.showTarget){ self.ctx.save(); self.ctx.beginPath(); self.ctx.arc(Math.round(this.targetX), Math.round(this.targetY), this.targetRadius, 0, Math.PI*2, false) self.ctx.closePath(); self.ctx.lineWidth = 1; self.ctx.stroke(); self.ctx.restore(); } if(self.showShockwave){ self.ctx.save(); self.ctx.translate(Math.round(this.x), Math.round(this.y)); self.ctx.rotate(this.shockwaveAngle); self.ctx.beginPath(); self.ctx.arc(0, 0, 1*(this.speed/5), 0, Math.PI, true); self.ctx.strokeStyle = 'hsla('+this.hue+', 100%, '+this.brightness+'%, '+rand(25, 60)/100+')'; self.ctx.lineWidth = this.lineWidth; self.ctx.stroke(); self.ctx.restore(); } };

这段JS代码是创建烟花实例的，我们也可以从draw方法中看出，当我们鼠标点击画布中的某点时，烟花发射的目的地就在那个点上。

这款HTML5 Canvas烟花效果的核心代码就是这样，全部的代码还请各位下载源代码研究。源代码下载>>