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tweenjs緩動(dòng)算法的使用實(shí)例分析

更新時(shí)間：2019年08月26日 10:42:21 作者：zhensg

這篇文章主要介紹了tweenjs緩動(dòng)算法的使用,結(jié)合實(shí)例形式分析了Tween.js插件的原理與使用技巧,需要的朋友可以參考下

本文實(shí)例講述了tweenjs緩動(dòng)算法的使用。分享給大家供大家參考，具體如下：

這里的tweenjs不是依托于createjs的tewwnjs，而是一系列緩動(dòng)算法集合。因?yàn)楸旧硎撬惴ǎ梢杂迷诟鱾€(gè)業(yè)務(wù)場(chǎng)景中，這也正是總結(jié)學(xué)習(xí)它的價(jià)值所在。tweenjs代碼詳情：

/*
 * Tween.js
 * t: current time（當(dāng)前時(shí)間）；
 * b: beginning value（初始值）；
 * c: change in value（變化量）；
 * d: duration（持續(xù)時(shí)間）。
 * 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;

具體每種算法的操作實(shí)例，可以看大神張?chǎng)涡竦牟┛蛯?shí)例：http://www.zhangxinxu.com/study/201612/how-to-use-tween-js.html

當(dāng)然，以上這些算法僅僅是一個(gè)狀態(tài)，需要配合時(shí)間上的變化，才能實(shí)現(xiàn)緩動(dòng)，這里使用的是requestAnimationFrame，具體代碼好吧，也是拿來主義

(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);
    };
}());

最后是簡(jiǎn)單的實(shí)例應(yīng)用，很簡(jiǎn)單，

<!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">
    這是測(cè)試
  </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,//開始時(shí)間
    b = 0,//開始位置
    c = 1000,//變化值
    d = 100;//持續(xù)時(shí)間
  var step = function() {
    var value = Tween.Bounce.easeOut(t, b, c, d);
    DOM.style.left = value + 'px';
    t++;
    if (t <= d) {
      // 繼續(xù)運(yùn)動(dòng)
      requestAnimationFrame(step);
    } else {
      // 動(dòng)畫結(jié)束
    }
  };
  step();
  </script>
</body>
</html>

具體使用中，需要參數(shù)以及控制好結(jié)束條件即可。

更多關(guān)于JavaScript相關(guān)內(nèi)容感興趣的讀者可查看本站專題：《JavaScript頁(yè)面元素操作技巧總結(jié)》、《JavaScript操作DOM技巧總結(jié)》、《JavaScript切換特效與技巧總結(jié)》、《JavaScript動(dòng)畫特效與技巧匯總》、《JavaScript錯(cuò)誤與調(diào)試技巧總結(jié)》、《JavaScript數(shù)據(jù)結(jié)構(gòu)與算法技巧總結(jié)》及《JavaScript數(shù)學(xué)運(yùn)算用法總結(jié)》

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