js+html5实现的自由落体运动效果代码

2019-11-20 10:40:08

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本文实例讲述了js+html5实现的自由落体运动效果。分享给大家供大家参考，具体如下：

运行效果截图如下：

具体代码如下：

<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head> <title>canvas自由落体</title> <script type="text/javascript" >  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 >= 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 <= 0) {     _self.vo = 0;     _self.y = y;     _self.prevTime = new Date().getTime();     if (y + _self.height < 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();  } </script></head><body><center><canvas id="canvas" width="500" height="500" style="background:#DDDDDD" ></canvas></center><input type="button" value="stop" onclick="stop()" /><input type="button" value="start" onclick="start()" /></body></html>

更多关于JavaScript运动相关内容感兴趣的读者可查看本站专题：《JavaScript运动效果与技巧汇总》

希望本文所述对大家JavaScript程序设计有所帮助。

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