利用requestAnimationFrame和Tween算法实现兼容所有浏览器的运动动画，直接秒杀Css3动画

以下贴出Tween的代码：

/*
 * 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;

requestAnimationFrame兼容性代码：

(function() {
    var lastTime = 0;
    var vendors = ['webkit', 'moz'];
    for(var x = 0; x < vendors.length && !window.requestAnimationFrame; ++x) {
        window.requestAnimationFrame = window[vendors[x] + 'RequestAnimationFrame'];
        window.cancelAnimationFrame = window[vendors[x] + 'CancelAnimationFrame'] ||    // name has changed in Webkit
                                      window[vendors[x] + 'CancelRequestAnimationFrame'];
    }

    if (!window.requestAnimationFrame) {
        window.requestAnimationFrame = function(callback, element) {
            var currTime = new Date().getTime();
            var timeToCall = Math.max(0, 16.7 - (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);
        };
    }
}());

调用方式和setTime类似

实际案例：

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>requestAnimationFrame实现皮球落地的缓动效果</title>
<script>
document.createElement("ball");
document.createElement("shadow");
</script>
<style>
.demo {
    height: 600px;
    position: relative;
}
h4 {
    text-align: center;
    font-size: 110%;
}
ball {
    width: 100px; height: 100px; border-radius: 100px;
    position: absolute; left: 50%; top: 500px;
    margin-left: -50px;
    background-color: #34538b;
    background-image: -webkit-radial-gradient(100px 100px at 50px 20px, #a0b3d6, #34538b);
    background-image:    -moz-radial-gradient(100px 100px at 50px 20px, #a0b3d6, #34538b);
    background-image:         radial-gradient(100px 100px at 50px 20px, #a0b3d6, #34538b);
    cursor: move;
    z-index: 1;
}
shadow {
    position: absolute;
    width: 100px; height: 30px;
    position: absolute; left: 50%; bottom: 5px;
    margin-left: -50px;
    background-image: -webkit-radial-gradient(ellipse closest-side, rgba(0,0,0,.75), rgba(0,0,0,0));
    background-image:    -moz-radial-gradient(ellipse closest-side, rgba(0,0,0,.75), rgba(0,0,0,0));
    background-image:         radial-gradient(ellipse closest-side, rgba(0,0,0,.75), rgba(0,0,0,0));
}
</style>
</head>
<body>
<div id="main">
    <h1>requestAnimationFrame实现皮球落地的缓动效果实例页面</h1>
    <div id="body" class="light">
        <div id="content" class="show">
            <h3>展示</h3>
            <div class="demo">
                <h4>向上拖动小球然后放下</h4>
                <ball></ball><shadow></shadow>         
            </div>
        </div>       
    </div>
</div>
<script src="js/jquery.min.js"></script>
<script src="js/requestAnimationFrame.js"></script>
<script src="js/tween.js"></script>
<script>
var ball = $("ball"), shadow = $("shadow");
var objBall = {};
var shadowWithBall = function(top) {
    // 0 ~ 500
    var top = top || parseInt(ball.css("top")),
    scale = 1 + (500 - top) / 500;
    opacity = 1 - (500 - top) / 500;
    if (opacity < 0) opacity = 0;
    shadow.css("opacity", opacity)
    .css("WebkitTransform", "scale("+ [scale, scale].join(",") +")")
    .css("transform", "scale("+ [scale, scale].join(",") +")");
}, funFall = function() {
    var start = 0, during = 100;
    var _run = function() {
        start++;
        var top = Tween.Bounce.easeOut(start, objBall.top, 500 - objBall.top, during);
        ball.css("top", top);
        shadowWithBall(top);
        if (start < during) requestAnimationFrame(_run);
    };
    _run();
};
ball.bind("mousedown", function(event) {
    objBall.pageY = event.pageY;
    objBall.flagFollow = true;    
});
$(document).bind("mousemove", function(event) {
    if (objBall.flagFollow) {
        var pageY = event.pageY;
        console.log(objBall.pageY + " === " + pageY);
        objBall.top = 500 - (objBall.pageY - pageY);
        if (objBall.top < 0) {
            objBall.top = 0;
        } else if (objBall.top > 500) {
            objBall.top = 500;
        }
        //cosnole.log(objBall.top);
        ball.css("top", objBall.top);
        shadowWithBall(objBall.top);    
    }
});
$(document).bind("mouseup", function(event) {
    if (objBall.flagFollow) funFall();
    objBall.flagFollow = false;    
});
</script>
</body>
</html>