tweenjs缓动算法的使用实例分析

2019-11-19 10:57:55

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本文实例讲述了tweenjs缓动算法的使用。分享给大家供大家参考，具体如下：

这里的tweenjs不是依托于createjs的tewwnjs，而是一系列缓动算法集合。因为本身是算法，可以用在各个业务场景中，这也正是总结学习它的价值所在。tweenjs代码详情：

/* * Tween.js * t: current time（当前时间）； * b: beginning value（初始值）； * c: change in value（变化量）； * d: duration（持续时间）。 * you can visit 'http://easings.net/zh-cn' to get effect*/var Tween = {  Linear: function(t, b, c, d) {    return c * t / d + b;  },  Quad: {    easeIn: function(t, b, c, d) {      return c * (t /= d) * t + b;    },    easeOut: function(t, b, c, d) {      return -c *(t /= d)*(t-2) + b;    },    easeInOut: function(t, b, c, d) {      if ((t /= d / 2) < 1) return c / 2 * t * t + b;      return -c / 2 * ((--t) * (t-2) - 1) + b;    }  },  Cubic: {    easeIn: function(t, b, c, d) {      return c * (t /= d) * t * t + b;    },    easeOut: function(t, b, c, d) {      return c * ((t = t/d - 1) * t * t + 1) + b;    },    easeInOut: function(t, b, c, d) {      if ((t /= d / 2) < 1) return c / 2 * t * t*t + b;      return c / 2*((t -= 2) * t * t + 2) + b;    }  },  Quart: {    easeIn: function(t, b, c, d) {      return c * (t /= d) * t * t*t + b;    },    easeOut: function(t, b, c, d) {      return -c * ((t = t/d - 1) * t * t*t - 1) + b;    },    easeInOut: function(t, b, c, d) {      if ((t /= d / 2) < 1) return c / 2 * t * t * t * t + b;      return -c / 2 * ((t -= 2) * t * t*t - 2) + b;    }  },  Quint: {    easeIn: function(t, b, c, d) {      return c * (t /= d) * t * t * t * t + b;    },    easeOut: function(t, b, c, d) {      return c * ((t = t/d - 1) * t * t * t * t + 1) + b;    },    easeInOut: function(t, b, c, d) {      if ((t /= d / 2) < 1) return c / 2 * t * t * t * t * t + b;      return c / 2*((t -= 2) * t * t * t * t + 2) + b;    }  },  Sine: {    easeIn: function(t, b, c, d) {      return -c * Math.cos(t/d * (Math.PI/2)) + c + b;    },    easeOut: function(t, b, c, d) {      return c * Math.sin(t/d * (Math.PI/2)) + b;    },    easeInOut: function(t, b, c, d) {      return -c / 2 * (Math.cos(Math.PI * t/d) - 1) + b;    }  },  Expo: {    easeIn: function(t, b, c, d) {      return (t==0) ? b : c * Math.pow(2, 10 * (t/d - 1)) + b;    },    easeOut: function(t, b, c, d) {      return (t==d) ? b + c : c * (-Math.pow(2, -10 * t/d) + 1) + b;    },    easeInOut: function(t, b, c, d) {      if (t==0) return b;      if (t==d) return b+c;      if ((t /= d / 2) < 1) return c / 2 * Math.pow(2, 10 * (t - 1)) + b;      return c / 2 * (-Math.pow(2, -10 * --t) + 2) + b;    }  },  Circ: {    easeIn: function(t, b, c, d) {      return -c * (Math.sqrt(1 - (t /= d) * t) - 1) + b;    },    easeOut: function(t, b, c, d) {      return c * Math.sqrt(1 - (t = t/d - 1) * t) + b;    },    easeInOut: function(t, b, c, d) {      if ((t /= d / 2) < 1) return -c / 2 * (Math.sqrt(1 - t * t) - 1) + b;      return c / 2 * (Math.sqrt(1 - (t -= 2) * t) + 1) + b;    }  },  Elastic: {    easeIn: function(t, b, c, d, a, p) {      var s;      if (t==0) return b;      if ((t /= d) == 1) return b + c;      if (typeof p == "undefined") p = d * .3;      if (!a || a < Math.abs(c)) {        s = p / 4;        a = c;      } else {        s = p / (2 * Math.PI) * Math.asin(c / a);      }      return -(a * Math.pow(2, 10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;    },    easeOut: function(t, b, c, d, a, p) {      var s;      if (t==0) return b;      if ((t /= d) == 1) return b + c;      if (typeof p == "undefined") p = d * .3;      if (!a || a < Math.abs(c)) {        a = c;        s = p / 4;      } else {        s = p/(2*Math.PI) * Math.asin(c/a);      }      return (a * Math.pow(2, -10 * t) * Math.sin((t * d - s) * (2 * Math.PI) / p) + c + b);    },    easeInOut: function(t, b, c, d, a, p) {      var s;      if (t==0) return b;      if ((t /= d / 2) == 2) return b+c;      if (typeof p == "undefined") p = d * (.3 * 1.5);      if (!a || a < Math.abs(c)) {        a = c;        s = p / 4;      } else {        s = p / (2 *Math.PI) * Math.asin(c / a);      }      if (t < 1) return -.5 * (a * Math.pow(2, 10* (t -=1 )) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;      return a * Math.pow(2, -10 * (t -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p ) * .5 + c + b;    }  },  Back: {    easeIn: function(t, b, c, d, s) {      if (typeof s == "undefined") s = 1.70158;      return c * (t /= d) * t * ((s + 1) * t - s) + b;    },    easeOut: function(t, b, c, d, s) {      if (typeof s == "undefined") s = 1.70158;      return c * ((t = t/d - 1) * t * ((s + 1) * t + s) + 1) + b;    },    easeInOut: function(t, b, c, d, s) {      if (typeof s == "undefined") s = 1.70158;      if ((t /= d / 2) < 1) return c / 2 * (t * t * (((s *= (1.525)) + 1) * t - s)) + b;      return c / 2*((t -= 2) * t * (((s *= (1.525)) + 1) * t + s) + 2) + b;    }  },  Bounce: {    easeIn: function(t, b, c, d) {      return c - Tween.Bounce.easeOut(d-t, 0, c, d) + b;    },    easeOut: function(t, b, c, d) {      if ((t /= d) < (1 / 2.75)) {        return c * (7.5625 * t * t) + b;      } else if (t < (2 / 2.75)) {        return c * (7.5625 * (t -= (1.5 / 2.75)) * t + .75) + b;      } else if (t < (2.5 / 2.75)) {        return c * (7.5625 * (t -= (2.25 / 2.75)) * t + .9375) + b;      } else {        return c * (7.5625 * (t -= (2.625 / 2.75)) * t + .984375) + b;      }    },    easeInOut: function(t, b, c, d) {      if (t < d / 2) {        return Tween.Bounce.easeIn(t * 2, 0, c, d) * .5 + b;      } else {        return Tween.Bounce.easeOut(t * 2 - d, 0, c, d) * .5 + c * .5 + b;      }    }  }}Math.tween = Tween;

具体每种算法的操作实例，可以看大神张鑫旭的博客实例：http://www.zhangxinxu.com/study/201612/how-to-use-tween-js.html

当然，以上这些算法仅仅是一个状态，需要配合时间上的变化，才能实现缓动，这里使用的是requestAnimationFrame，具体代码好吧，也是拿来主义

(function() {  var lastTime = 0;  var vendors = ['ms', 'moz', 'webkit', 'o'];  for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {    window.requestAnimationFrame = window[vendors[x]+'RequestAnimationFrame'];    window.cancelAnimationFrame = window[vendors[x]+'CancelAnimationFrame']                  || window[vendors[x]+'CancelRequestAnimationFrame'];  }  if (!window.requestAnimationFrame)    window.requestAnimationFrame = function(callback, element) {      var currTime = new Date().getTime();      var timeToCall = Math.max(0, 16 - (currTime - lastTime));      var id = window.setTimeout(function() { callback(currTime + timeToCall); },       timeToCall);      lastTime = currTime + timeToCall;      return id;    };  if (!window.cancelAnimationFrame)    window.cancelAnimationFrame = function(id) {      clearTimeout(id);    };}());

最后是简单的实例应用，很简单，

<!DOCTYPE html><html lang="en"><head>  <meta charset="UTF-8">  <title>使用tweenjs</title>  <style type="text/css">  div {    width: 100px;    height: 100px;    border: 1px solid red;    text-align: center;    line-height: 100px;    position: absolute;  }  </style></head><body>  <div id="test">    这是测试  </div>  <script type="text/javascript" src="RequestAnimationFrame.js"></script>  <script type="text/javascript" src="tween.js"></script>  <script type="text/javascript">    var DOM=document.getElementById("test");  var t = 0,//开始时间    b = 0,//开始位置    c = 1000,//变化值    d = 100;//持续时间  var step = function() {    var value = Tween.Bounce.easeOut(t, b, c, d);    DOM.style.left = value + 'px';    t++;    if (t <= d) {      // 继续运动      requestAnimationFrame(step);    } else {      // 动画结束    }  };  step();  </script></body></html>

具体使用中，需要参数以及控制好结束条件即可。

更多关于JavaScript相关内容感兴趣的读者可查看本站专题：《JavaScript页面元素操作技巧总结》、《JavaScript操作DOM技巧总结》、《JavaScript切换特效与技巧总结》、《JavaScript动画特效与技巧汇总》、《JavaScript错误与调试技巧总结》、《JavaScript数据结构与算法技巧总结》及《JavaScript数学运算用法总结》

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