js实现点击烟花特效_JavaScript

代码：

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									<script type="text/javascript">

									function clickEffect() {

									  let balls = [];

									  let longPressed = false;

									  let longPress;

									  let multiplier = 0;

									  let width, height;

									  let origin;

									  let normal;

									  let ctx;

									  const colours = ["#F73859", "#14FFEC", "#00E0FF", "#FF99FE", "#FAF15D"];

									  const canvas = document.createElement("canvas");

									  document.body.appendChild(canvas);

									  canvas.setAttribute("style", "width: 100%; height: 100%; top: 0; left: 0; z-index: 99999; position: fixed; pointer-events: none;");

									  const pointer = document.createElement("span");

									  pointer.classList.add("pointer");

									  document.body.appendChild(pointer);

									  if (canvas.getContext && window.addEventListener) {

									    ctx = canvas.getContext("2d");

									    updateSize();

									    window.addEventListener('resize', updateSize, false);

									    loop();

									    window.addEventListener("mousedown", function(e) {

									      pushBalls(randBetween(10, 20), e.clientX, e.clientY);

									      document.body.classList.add("is-pressed");

									      longPress = setTimeout(function() {

									        document.body.classList.add("is-longpress");

									        longPressed = true;

									      }, 500);

									    }, false);

									    window.addEventListener("mouseup", function(e) {

									      clearInterval(longPress);

									      if (longPressed == true) {

									        document.body.classList.remove("is-longpress");

									        pushBalls(randBetween(50 + Math.ceil(multiplier), 100 + Math.ceil(multiplier)), e.clientX, e.clientY);

									        longPressed = false;

									      }

									      document.body.classList.remove("is-pressed");

									    }, false);

									    window.addEventListener("mousemove", function(e) {

									      let x = e.clientX;

									      let y = e.clientY;

									      pointer.style.top = y + "px";

									      pointer.style.left = x + "px";

									    }, false);

									  } else {

									    console.log("canvas or addEventListener is unsupported!");

									  }

									  function updateSize() {

									    canvas.width = window.innerWidth * 2;

									    canvas.height = window.innerHeight * 2;

									    canvas.style.width = window.innerWidth + 'px';

									    canvas.style.height = window.innerHeight + 'px';

									    ctx.scale(2, 2);

									    width = (canvas.width = window.innerWidth);

									    height = (canvas.height = window.innerHeight);

									    origin = {

									      x: width / 2,

									      y: height / 2

									    };

									    normal = {

									      x: width / 2,

									      y: height / 2

									    };

									  }

									  class Ball {

									    constructor(x = origin.x, y = origin.y) {

									      this.x = x;

									      this.y = y;

									      this.angle = Math.PI * 2 * Math.random();

									      if (longPressed == true) {

									        this.multiplier = randBetween(14 + multiplier, 15 + multiplier);

									      } else {

									        this.multiplier = randBetween(6, 12);

									      }

									      this.vx = (this.multiplier + Math.random() * 0.5) * Math.cos(this.angle);

									      this.vy = (this.multiplier + Math.random() * 0.5) * Math.sin(this.angle);

									      this.r = randBetween(8, 12) + 3 * Math.random();

									      this.color = colours[Math.floor(Math.random() * colours.length)];

									    }

									    update() {

									      this.x += this.vx - normal.x;

									      this.y += this.vy - normal.y;

									      normal.x = -2 / window.innerWidth * Math.sin(this.angle);

									      normal.y = -2 / window.innerHeight * Math.cos(this.angle);

									      this.r -= 0.3;

									      this.vx *= 0.9;

									      this.vy *= 0.9;

									    }

									  }

									  function pushBalls(count = 1, x = origin.x, y = origin.y) {

									    for (let i = 0; i < count; i++) {

									      balls.push(new Ball(x, y));

									    }

									  }

									  function randBetween(min, max) {

									    return Math.floor(Math.random() * max) + min;

									  }

									  function loop() {

									    ctx.fillStyle = "rgba(255, 255, 255, 0)";

									    ctx.clearRect(0, 0, canvas.width, canvas.height);

									    for (let i = 0; i < balls.length; i++) {

									      let b = balls[i];

									      if (b.r < 0) continue;

									      ctx.fillStyle = b.color;

									      ctx.beginPath();

									      ctx.arc(b.x, b.y, b.r, 0, Math.PI * 2, false);

									      ctx.fill();

									      b.update();

									    }

									    if (longPressed == true) {

									      multiplier += 0.2;

									    } else if (!longPressed && multiplier >= 0) {

									      multiplier -= 0.4;

									    }

									    removeBall();

									    requestAnimationFrame(loop);

									  }

									  function removeBall() {

									    for (let i = 0; i < balls.length; i++) {

									      let b = balls[i];

									      if (b.x + b.r < 0 || b.x - b.r > width || b.y + b.r < 0 || b.y - b.r > height || b.r < 0) {

									        balls.splice(i, 1);

									      }

									    }

									  }

									}

									clickEffect();//调用

									</script>