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：
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，
使用tweenjs div { width: 100px; height: 100px; border: 1px solid red; text-align: center; line-height: 100px; position: absolute; } 这是测试
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》
希望本文所述对大家Javascript程序设计有所帮助。
