Free fall motion effect code implemented by js+html5_javascript skills-JS Tutorial-php.cn

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Free fall motion effect code implemented by js+html5_javascript skills

May 16, 2016 pm 03:17 PM

html5 js

The example in this article describes the free fall motion effect achieved by js+html5. Share it with everyone for your reference, the details are as follows:

The screenshot of the running effect is as follows:

The specific code is as follows:

&lt;!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN"
"http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"&gt;
&lt;html xmlns="http://www.w3.org/1999/xhtml"&gt;
&lt;head&gt;
 &lt;title&gt;canvas自由落体&lt;/title&gt;
 &lt;script type="text/javascript" &gt;
  var canvasheight = 500;
  var canvaswidth = 500;
  var g = 9.8;
  var plusV = 0.5;
  function Block(vo, x, y, width, height, g, context) {
   var _self = this;
   _self.vo = vo || 0;
   _self.x = x;
   _self.y = y;
   _self.prevX = x;
   _self.prevY = y;
   _self.g = g;
   _self.height = height;
   _self.width = width;
   _self.prevTime = new Date().getTime();
   context.fillStyle = "black";
   _self.down = function () {
    var time = (new Date().getTime() - _self.prevTime) / 200,
     y = _self.vo * time + 1 / 2 * _self.g * time * time + _self.y;
    //console.log("down:time=" + time + ":y=" + y + ":" + _self.vo);
    if (y + _self.height &gt;= canvasheight) {
     _self.g--;
     _self.vo = _self.g * time;
     _self.prevTime = new Date().getTime();
     _self.up();
    } else {
     context.clearRect(_self.prevX, _self.prevY - 1, _self.prevX + _self.height, _self.prevY + _self.width);
     context.fillRect(_self.x, y, _self.width, _self.height);
     _self.prevX = x;
     _self.prevY = y;
     setTimeout(function () {
      _self.down();
     }, 30);
    }
   }
   _self.up = function () {
    var time = (new Date().getTime() - _self.prevTime) / 200,
     v = _self.vo - _self.g * time,
     y = canvasheight - _self.height - _self.vo * time + 1 / 2 * _self.g * time * time;
    //console.log("up:time=" + time + ":v=" + v);
    if (v &lt;= 0) {
     _self.vo = 0;
     _self.y = y;
     _self.prevTime = new Date().getTime();
     if (y + _self.height &lt; canvasheight) {
      _self.down();
     } else {
      return;
     }
    } else {
     context.clearRect(_self.prevX, _self.prevY - 1, _self.prevX + _self.height , _self.prevY + _self.width);
     context.fillRect(x, y, _self.width, _self.height);
     _self.prevX = x;
     _self.prevY = y;
     setTimeout(function () {
      _self.up();
     }, 30);
    }
   }
  }
  window.onload = function () {
   var canvas = document.getElementById('canvas');
   var context = canvas.getContext('2d');
   height = canvas.offsetHeight;
   var block = new Block(0, 100, 0, 20, 20, g, context);
   block.down();
  }
 &lt;/script&gt;
&lt;/head&gt;
&lt;body&gt;
&lt;center&gt;
&lt;canvas id="canvas" width="500" height="500" style="background:#DDDDDD" &gt;&lt;/canvas&gt;
&lt;/center&gt;
&lt;input type="button" value="stop" onclick="stop()" /&gt;
&lt;input type="button" value="start" onclick="start()" /&gt;
&lt;/body&gt;
&lt;/html&gt;

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Readers who are interested in more content related to JavaScript sports can check out the special topic on this site: " Summary of JavaScript sports effects and techniques"

I hope this article will be helpful to everyone in JavaScript programming.

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