JS绘制电流闪烁流动效果

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>电流闪动动效</title>
    <style>
        .sd1 {
            display: block;
            margin: 0 auto;
            background-color: black;
        }
        .sd2 {
            display: block;
            margin: 0 auto;
            background-color: black;
        }
        .sd3 {
            display: block;
            margin: 0 auto;
            background-color: black;
        }
    </style>
</head>
<body>
    <div class="sd1"></div>
    <div class="sd2"></div>
    <div class="sd3"></div>
    <script>
        var ele='.sd1';
        var ele2='.sd2';
        var ele3='.sd3';
        sd1(ele);
        sd1(ele2);
        sd1(ele3);
  function sd1(ele) {
        var width, height
        var step = 0;
        var canvas = document.createElement('canvas')
        var ctx = canvas.getContext('2d')

        var bg = [4, 10, 11]
        document.querySelector(ele).appendChild(canvas)
        setTimeout(() => {
            var timeID = setInterval(() => {
                pt1.x += 10;
                if (pt1.x > width - 10) {
                    clearInterval(timeID)
                }
            }, 60);
        }, 1000)

        var pt1
        var pt2

        window.addEventListener('resize', setup)

        setup()

        function setup() {
            canvas.width = width = document.querySelector(ele).clientWidth
            canvas.height = height = document.querySelector(ele).clientHeight

            ctx.beginPath();
            ctx.rect(0, 0, width, height)
            ctx.fillStyle = `rgba(${bg[0]}, ${bg[1]}, ${bg[2]}, ${1})`
            ctx.fill()

            pt1 = { x: -20, y: height / 2 }//闪电起点
            pt2 = { x: -20, y: height / 2 } //闪电终点
        }

        setInterval(animate, 60)

        function blur(ctx, canvas, amt) {
            ctx.filter = `blur(${amt}px)`
            ctx.drawImage(canvas, 0, 0)
            ctx.filter = 'none'
        }

        function fade(ctx, amt, width, height) {
            ctx.beginPath();
            ctx.rect(0, 0, width, height)
            ctx.fillStyle = `rgba(${bg[0]}, ${bg[1]}, ${bg[2]}, ${amt})`
            ctx.fill()
        }

        function animate() {
            step++

            blur(ctx, canvas, 1)
            draw()
            fade(ctx, 0.1, width, height)

         }

        function draw() {

            var iterations = [pt1, pt2]
            var newiterations, i, j
            for (i = 0; i < 8; i++) {
                newiterations = [iterations[0]]
                for (j = 1; j < iterations.length; j++) {
                    newiterations.push(getRandMidpoint(iterations[j - 1], iterations[j], 200 / (i * i + 1)))
                    newiterations.push(iterations[j])
                }
                iterations = newiterations.concat([])
            }
            ctx.beginPath();
            ctx.moveTo(iterations[0].x, iterations[0].y);
            ctx.lineWidth = 2;
            ctx.strokeStyle = '#04e4c9';
            for (i = 1; i < iterations.length; i++) {
                ctx.lineTo(iterations[i].x, iterations[i].y);
            }
            ctx.stroke()
            ctx.closePath()
        }

        function getRandMidpoint(pa, pb, range) {
            var a = Math.atan2(pb.y - pa.y, pb.x - pa.x) + Math.PI / 2
            var half = { y: (pb.y - pa.y) / 2 + pa.y, x: (pb.x - pa.x) / 2 + pa.x }
            var offset = Math.random() * range / 3 - range / 6  //这里控制闪电的抖动幅度
            var ho = {
                x: Math.cos(a) * offset + half.x,
                y: Math.sin(a) * offset + half.y
            }
            return ho
        }
    }
    </script>
</body>
</html>

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