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Detailed explanation of the steps to implement snowflake falling animation with JS

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Release: 2018-06-01 11:33:07
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This time I will bring you a detailed explanation of the steps to implement the snowflake falling animation with JS. What are the precautions for implementing the snowflake falling animation with JS. The following is a practical case, let’s take a look.

<!DOCTYPE html>
<html>
<head>
  <meta charset="utf-8">
  <meta http-equiv="X-UA-Compatible" content="IE=edge">
  <title>JS下雪动画</title>
  <meta name="description" content="">
  <meta name="viewport" content="width=device-width, initial-scale=1">
</head>
<style>
  .masthead {
    background-color:#333;
    display:block;
    width:100%;
    height:400px;
  }
</style>
<body>
<p class="masthead"></p>
<script>
  (function () {
    var COUNT = 300;
    var masthead = document.querySelector('.masthead');
    var canvas = document.createElement('canvas');
    var ctx = canvas.getContext('2d');
    var width = masthead.clientWidth;
    var height = masthead.clientHeight;
    var i = 0;
    var active = false;
    function onResize() {
      width = masthead.clientWidth;
      height = masthead.clientHeight;
      canvas.width = width;
      canvas.height = height;
      ctx.fillStyle = '#FFF';
      var wasActive = active;
      active = width > 600;
      if (!wasActive && active)
        requestAnimFrame(update);
    }
    var Snowflake = function () {
      this.x = 0;
      this.y = 0;
      this.vy = 0;
      this.vx = 0;
      this.r = 0;
      this.reset();
    };
    Snowflake.prototype.reset = function() {
      this.x = Math.random() * width;
      this.y = Math.random() * -height;
      this.vy = 1 + Math.random() * 3;
      this.vx = 0.5 - Math.random();
      this.r = 1 + Math.random() * 2;
      this.o = 0.5 + Math.random() * 0.5;
    };
    canvas.style.position = 'absolute';
    canvas.style.left = canvas.style.top = '0';
    var snowflakes = [], snowflake;
    for (i = 0; i < COUNT; i++) {
      snowflake = new Snowflake();
      snowflakes.push(snowflake);
    }
    function update() {
      ctx.clearRect(0, 0, width, height);
      if (!active)
        return;
      for (i = 0; i < COUNT; i++) {
        snowflake = snowflakes[i];
        snowflake.y += snowflake.vy;
        snowflake.x += snowflake.vx;
        ctx.globalAlpha = snowflake.o;
        ctx.beginPath();
        ctx.arc(snowflake.x, snowflake.y, snowflake.r, 0, Math.PI * 2, false);
        ctx.closePath();
        ctx.fill();
        if (snowflake.y > height) {
          snowflake.reset();
        }
      }
      requestAnimFrame(update);
    }
    // shim layer with setTimeout fallback
    window.requestAnimFrame = (function(){
      return window.requestAnimationFrame    ||
          window.webkitRequestAnimationFrame ||
          window.mozRequestAnimationFrame  ||
          function( callback ){
            window.setTimeout(callback, 1000 / 60);
          };
    })();
    onResize();
    window.addEventListener('resize', onResize, false);
    masthead.appendChild(canvas);
  })();
</script></body></html>
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Use this siteHTML/CSS/JS online running test tool: http://tools.jb51.net/code/HtmlJsRun, you can get the following test Operation effect:

# I believe you have mastered the method after reading the case in this article. For more exciting information, please pay attention to other related articles on the PHP Chinese website!

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The above is the detailed content of Detailed explanation of the steps to implement snowflake falling animation with JS. For more information, please follow other related articles on the PHP Chinese website!

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