js实现跟随鼠标粒子效果

以下是一个简单的js代码实现跟随鼠标粒子效果：

HTML：

<canvas id="canvas"></canvas>

CSS：

#canvas {
    position: absolute;
    top: 0;
    left: 0;
    width: 100%;
    height: 100%;
}

JS：

var canvas = document.getElementById("canvas");
var ctx = canvas.getContext("2d");
var particles = [];

var mouse = {
    x: undefined,
    y: undefined
}

window.addEventListener("mousemove", function(event) {
    mouse.x = event.x;
    mouse.y = event.y;
});

function Particle(x, y, radius, color) {
    this.x = x;
    this.y = y;
    this.radius = radius;
    this.color = color;
    this.radians = Math.random() * Math.PI * 2;
    this.velocity = 0.05;
    this.distanceFromCenter = Math.random() * 50 + 100;
    this.lastMouse = {x: x, y: y};

    this.draw = function(lastPoint) {
        ctx.beginPath();
        ctx.strokeStyle = this.color;
        ctx.lineWidth = this.radius;
        ctx.moveTo(lastPoint.x, lastPoint.y);
        ctx.lineTo(this.x, this.y);
        ctx.stroke();
        ctx.closePath();
    }

    this.update = function() {
        // 记录上一帧的鼠标位置
        this.lastMouse.x += (mouse.x - this.lastMouse.x) * 0.05;
        this.lastMouse.y += (mouse.y - this.lastMouse.y) * 0.05;

        // 运动轨迹
        this.radians += this.velocity;
        this.x = this.lastMouse.x + Math.cos(this.radians) * this.distanceFromCenter;
        this.y = this.lastMouse.y + Math.sin(this.radians) * this.distanceFromCenter;
        this.draw(this.lastMouse);
    }
}

function init() {
    canvas.width = window.innerWidth;
    canvas.height = window.innerHeight;

    for (var i = 0; i < 50; i++) {
        var radius = Math.random() * 3 + 1;
        var color = "rgba(255, 255, 255, 0.5)";
        particles.push(new Particle(canvas.width / 2, canvas.height / 2, radius, color));
    }
}

function animate() {
    requestAnimationFrame(animate);
    ctx.fillStyle = "rgba(0, 0, 0, 0.1)";
    ctx.fillRect(0, 0, canvas.width, canvas.height);

    for (var i = 0; i < particles.length; i++) {
        particles[i].update();
    }
}

init();
animate();

这段代码创建了一个画布，并且在鼠标移动时跟随鼠标移动的粒子效果。