特效描述：利用HTML5实现庆祝2018年烟花动画特效。利用HTML5实现庆祝2018年烟花动画特效

代码结构

1. HTML代码

2018

var ctx = document.querySelector('canvas').getContext('2d')

ctx.canvas.width = window.innerWidth

ctx.canvas.height = window.innerHeight

var sparks = []

var fireworks = []

var i = 20; while(i--) {

fireworks.push(

new Firework(Math.random()*window.innerWidth, window.innerHeight*Math.random())

)

}

render()

function render() {

setTimeout(render, 1000/60)

ctx.fillStyle = 'rgba(0, 0, 0, 0.1)';

ctx.fillRect(0, 0, ctx.canvas.width, ctx.canvas.height)

for(var firework of fireworks) {

if(firework.dead) continue

firework.move()

firework.draw()

}

for(var spark of sparks) {

if(spark.dead) continue

spark.move()

spark.draw()

}

if(Math.random() < 0.05) {

fireworks.push(new Firework())

}

}

function Spark(x, y, color) {

this.x = x

this.y = y

this.dir = Math.random() * (Math.PI*2)

this.dead = false

this.color = color

this.speed = Math.random() * 3 + 3;

this.walker = new Walker({ radius: 20, speed: 0.25 })

this.gravity = 0.25

this.dur = this.speed / 0.1

this.move = function() {

this.dur--

if(this.dur < 0) this.dead = true

if(this.speed < 0) return

if(this.speed > 0) this.speed -= 0.1

var walk = this.walker.step()

this.x += Math.cos(this.dir + walk) * this.speed

this.y += Math.sin(this.dir + walk) * this.speed

this.y += this.gravity

this.gravity += 0.05

}

this.draw = function() {

drawCircle(this.x, this.y, 3, this.color)

}

}

function Firework(x, y) {

this.xmove = new Walker({radius: 10, speed: 0.5})

this.x = x || Math.random() * ctx.canvas.width

this.y = y || ctx.canvas.height

this.height = Math.random()*ctx.canvas.height/2

this.dead = false

this.color = randomColor()

this.move = function() {

this.x += this.xmove.step()

if(this.y > this.height) this.y -= 1;

else this.burst()

}

this.draw = function() {

drawCircle(this.x, this.y, 1, this.color)

}

this.burst = function() {

this.dead = true

var i = 100; while(i--) sparks.push(new Spark(this.x, this.y, this.color))

}

}

function drawCircle(x, y, radius, color) {

color = color || '#FFF'

ctx.fillStyle = color

ctx.fillRect(x-radius/2, y-radius/2, radius, radius)

}

function randomColor(){

return ['#6ae5ab','#88e3b2','#36b89b','#7bd7ec','#66cbe1'][Math.floor(Math.random() * 5)];

}

function Walker(options){

this.step = function(){

this.direction = Math.sign(this.target) * this.speed

this.value += this.direction

this.target

? this.target -= this.direction

: (this.value)

? (this.wander)

? this.target = this.newTarget()

: this.target = -this.value

: this.target = this.newTarget()

return this.direction

}

this.newTarget = function() {

return Math.round(Math.random()*(this.radius*2)-this.radius)

}

this.start = 0

this.value = 0

this.radius = options.radius

this.target = this.newTarget()

this.direction = Math.sign(this.target)

this.wander = options.wander

this.speed = options.speed || 1

}