canvas实现流星效果

效果如下
存储每个星星对象
绘制单个星星，内圆和外圆点的连线
绘制一堆星星
更新星星位置
完整代码
<!DOCTYPE html>
<html lang="en">

<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>流星</title>
    <style>
        html,
        body {
            margin: 0;
            padding: 0;
        }

        #canvas {
            background-color: rgba(0,0,0,1);
        }
    </style>
</head>

<body>
    <canvas id="canvas"></canvas>
    <script>
        window.addEventListener("load", function () {
            var canvas = document.getElementById("canvas");
            var ctx = canvas.getContext("2d");
            var arr = [];//存储星星

            window.addEventListener("resize", resizeFn)
            function resizeFn() {
                canvas.width = window.innerWidth;
                canvas.height = window.innerHeight;
            }
            resizeFn();
            
            canvas.style.cssText = `
                position: fixed;
                z-index: 1000;
                pointer-events: none;
            `;

            setInterval(() => {
                arr.push({
                    x: canvas.width - Math.floor(Math.random() * canvas.width),
                    y: 0,
                    r: Math.random() * 2.5 + 2.5,//星星内圆半径
                    td: Math.random() * 5,//旋转角度
                    dx: 8,//x轴移动距离
                    dy: 8,//y轴移动距离
                    rot: Math.random() * 90 + 90,// 初始的旋转角度
                    color: "yellow"
                });
            },50)
            
            // 绘制单个星星
            function single(x, y, r, l, rot) {
                ctx.beginPath();
                // 循环5次，因为5个点
                for (let i = 0; i < 5; i++) {
                    //先绘制小圆上一个点       
                    ctx.lineTo(Math.cos((18 + i * 72 - rot) * Math.PI / 180) * r + x,
                        -Math.sin((18 + i * 72 - rot) * Math.PI / 180) * r + y);
                    //连线到大圆上一个点
                    ctx.lineTo(Math.cos((54 + i * 72 - rot) * Math.PI / 180) * l + x
                        , -Math.sin((54 + i * 72 - rot) * Math.PI / 180) * l + y);
                }
                ctx.closePath(); 
            }

            // 绘制一堆星星
            function draw() {
                //循环数组
                for (let i = 0; i < arr.length; i++) {
                    let temp = arr[i];
                    //调用绘制一个星星函数
                    single(temp.x, temp.y, temp.r, temp.r * 2, temp.rot);
                    //星星颜色
                    ctx.fillStyle = temp.color;
                    //星星边框颜色
                    ctx.strokeStyle = temp.color;
                    //线宽度
                    ctx.lineWidth = 0.1;
                    //角有弧度
                    ctx.lineJoin = "round";
                    // 填充
                    ctx.fill();
                    // 绘制路径
                    ctx.stroke();
                }
            }

            function update(){
                 //循环数组
                 for (let i = 0; i < arr.length; i++) {
                    arr[i].x -= arr[i].dx;
                    arr[i].y += arr[i].dy;
                    arr[i].rot += arr[i].td;

                    if(arr[i].r < 0) arr.splice(i,1);
                }
            }

            setInterval(() => {
                //清屏
                ctx.fillStyle = "rgba(0,0,0,0.1)";
                ctx.fillRect(0,0,canvas.width, canvas.height);

                draw();
                update();
            })

        })
    </script>
</body>

</html>
canvas实现流星效果

悦读
