前端实现雪花效果，粒子特效

<template>
    <div id="main">
        <canvas id="canvas" ref="canvas" style="z-index: 100;position: fixed;top: 0;width: 100%;height: 90%;">
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        </canvas>
    </div>
</template>
 
<script>
//  import Footer from '@/components/Footer.vue'
 
    export default {
        components: {
//          Footer
        },
        data() {
            return { //canvas init
                canvas: "",
                ctx: "",
                W: "",
                H: "",
                angle: 0,
                mp: 3000,
                particles: [],
                t: 0,
            }
        },
        mounted() {
            this._initCavas();
        },
        methods: {
            _initCavas() {
                this.canvas = document.getElementById("canvas");
                this.ctx = this.canvas.getContext("2d");
 
                //canvas dimensions
                this.W = window.innerWidth - 30;
                this.H = window.innerHeight - 10;
                this.canvas.width = this.W;
                this.canvas.height = this.H;
 
                //snowflake particles
                  //雪花数量
                this.mp = 500;
                this.particles = [];
                for (var i = 0; i < this.mp; i++) {
                    this.particles.push({
                        x: Math.random() * this.W * 5, //x-coordinate
                        y: Math.random() * this.H, //y-coordinate
                        //改变大小
                        r: Math.random() * 1 + 1, //radius
                        d: Math.random() * this.mp //density
                    })
                }
                clearInterval(localStorage.getItem('interval'));
                localStorage.setItem('interval', setInterval(this.draw, 25));
            },
            draw() {
                this.ctx.clearRect(0, 0, this.W, this.H);
 
                this.ctx.fillStyle = "rgba(37, 211, 236)";
                this.ctx.fillStyle = "border: 1px solid rgb(37, 211, 236,0.2)";
                this.ctx.fillStyle = "box-shadow: 0px 0px 3px rgb(37, 211, 236,0.5)";
                this.ctx.beginPath();
                for (var i = 0; i < this.mp; i++) {
                    var p = this.particles[i];
                    this.ctx.moveTo(p.x, p.y);
                    this.ctx.arc(p.x, p.y, p.r, 0, Math.PI * 2, true);
                }
                this.ctx.fill();
                this.update();
            },
            update() {
//              this.angle += 0.01;
                for (var i = 0; i < this.mp; i++) {
                    var p = this.particles[i];
                    p.y += Math.cos(this.angle + p.d) + 1 + p.r / 2;
                    p.x += Math.sin(this.angle) * 2;
 
                    if (p.x > this.W || p.x < 0 || p.y > this.H) {
                        if (i % 3 > 0) {
                            this.particles[i] = {
                                x: Math.random() * this.W,
                                y: -10,
                                r: p.r,
                                d: p.d
                            };
                        } else {
                            if (Math.sin(this.angle) > 0) {
                                //Enter fromth
                                this.particles[i] = {
                                    x: -5,
                                    y: Math.random() * this.H,
                                    r: p.r,
                                    d: p.d
                                };
                            } else {
                                this.particles[i] = {
                                    x: this.W + 5,
                                    y: Math.random() * this.H,
                                    r: p.r,
                                    d: p.d
                                };
                            }
                        }
                    }
                }
            }
        }
    }
</script>
 
<style>
    #main {
        margin: 0;
        padding: 0;
        width: 100%;
        height: 100%;
        background: url(../../assets/img/aaaa.png);
        z-index: 999;
        background-repeat: no-repeat;
        position: absolute;
        background-size: 100% 100%;
    }
</style>