一些插值函数 easy

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/* ============================================================

• jQuery Easing v1.3 - http://gsgd.co.uk/sandbox/jquery/easing/
• Open source under the BSD License.
• Copyright © 2008 George McGinley Smith
• All rights reserved.
• https://raw.github.com/danro/jquery-easing/master/LICENSE
• ======================================================== */

jQuery.easing['jswing'] = jQuery.easing['swing'];

jQuery.extend( jQuery.easing,
{
// t: current time, b: begInnIng value, c: change In value, d: duration

def: 'easeOutQuad',
swing: function (x, t, b, c, d) {
    //alert(jQuery.easing.default);
    return jQuery.easing[jQuery.easing.def](x, t, b, c, d);
},
easeInQuad: function (x, t, b, c, d) {
    return c*(t/=d)*t + b;
},
easeOutQuad: function (x, t, b, c, d) {
    return -c *(t/=d)*(t-2) + b;
},
easeInOutQuad: function (x, t, b, c, d) {
    if ((t/=d/2) < 1) return c/2*t*t + b;
    return -c/2 * ((--t)*(t-2) - 1) + b;
},
easeInCubic: function (x, t, b, c, d) {
    return c*(t/=d)*t*t + b;
},
easeOutCubic: function (x, t, b, c, d) {
    return c*((t=t/d-1)*t*t + 1) + b;
},
easeInOutCubic: function (x, 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;
},
easeInQuart: function (x, t, b, c, d) {
    return c*(t/=d)*t*t*t + b;
},
easeOutQuart: function (x, t, b, c, d) {
    return -c * ((t=t/d-1)*t*t*t - 1) + b;
},
easeInOutQuart: function (x, 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;
},
easeInQuint: function (x, t, b, c, d) {
    return c*(t/=d)*t*t*t*t + b;
},
easeOutQuint: function (x, t, b, c, d) {
    return c*((t=t/d-1)*t*t*t*t + 1) + b;
},
easeInOutQuint: function (x, 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;
},
easeInSine: function (x, t, b, c, d) {
    return -c * Math.cos(t/d * (Math.PI/2)) + c + b;
},
easeOutSine: function (x, t, b, c, d) {
    return c * Math.sin(t/d * (Math.PI/2)) + b;
},
easeInOutSine: function (x, t, b, c, d) {
    return -c/2 * (Math.cos(Math.PI*t/d) - 1) + b;
},
easeInExpo: function (x, t, b, c, d) {
    return (t==0) ? b : c * Math.pow(2, 10 * (t/d - 1)) + b;
},
easeOutExpo: function (x, t, b, c, d) {
    return (t==d) ? b+c : c * (-Math.pow(2, -10 * t/d) + 1) + b;
},
easeInOutExpo: function (x, 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;
},
easeInCirc: function (x, t, b, c, d) {
    return -c * (Math.sqrt(1 - (t/=d)*t) - 1) + b;
},
easeOutCirc: function (x, t, b, c, d) {
    return c * Math.sqrt(1 - (t=t/d-1)*t) + b;
},
easeInOutCirc: function (x, 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;
},
easeInElastic: function (x, t, b, c, d) {
    var s=1.70158;var p=0;var a=c;
    if (t==0) return b;  if ((t/=d)==1) return b+c;  if (!p) p=d*.3;
    if (a < Math.abs(c)) { a=c; var s=p/4; }
    else var 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;
},
easeOutElastic: function (x, t, b, c, d) {
    var s=1.70158;var p=0;var a=c;
    if (t==0) return b;  if ((t/=d)==1) return b+c;  if (!p) p=d*.3;
    if (a < Math.abs(c)) { a=c; var s=p/4; }
    else var 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;
},
easeInOutElastic: function (x, t, b, c, d) {
    var s=1.70158;var p=0;var a=c;
    if (t==0) return b;  if ((t/=d/2)==2) return b+c;  if (!p) p=d*(.3*1.5);
    if (a < Math.abs(c)) { a=c; var s=p/4; }
    else var 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;
},
easeInBack: function (x, t, b, c, d, s) {
    if (s == undefined) s = 1.70158;
    return c*(t/=d)*t*((s+1)*t - s) + b;
},
easeOutBack: function (x, t, b, c, d, s) {
    if (s == undefined) s = 1.70158;
    return c*((t=t/d-1)*t*((s+1)*t + s) + 1) + b;
},
easeInOutBack: function (x, t, b, c, d, s) {
    if (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;
},
easeInBounce: function (x, t, b, c, d) {
    return c - jQuery.easing.easeOutBounce (x, d-t, 0, c, d) + b;
},
easeOutBounce: function (x, 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;
    }
},
easeInOutBounce: function (x, t, b, c, d) {
    if (t < d/2) return jQuery.easing.easeInBounce (x, t*2, 0, c, d) * .5 + b;
    return jQuery.easing.easeOutBounce (x, t*2-d, 0, c, d) * .5 + c*.5 + b;
}

});

/*

• TERMS OF USE - EASING EQUATIONS
• Open source under the BSD License.
• Copyright © 2001 Robert Penner
• All rights reserved.
• Redistribution and use in source and binary forms, with or without modification,
• are permitted provided that the following conditions are met:
• Redistributions of source code must retain the above copyright notice, this list of
• conditions and the following disclaimer.
• Redistributions in binary form must reproduce the above copyright notice, this list
• of conditions and the following disclaimer in the documentation and/or other materials
• provided with the distribution.
• Neither the name of the author nor the names of contributors may be used to endorse
• or promote products derived from this software without specific prior written permission.
• THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS" AND ANY
• EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES OF
• MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
• COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
• EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE
• GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
• AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
• NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED
• OF THE POSSIBILITY OF SUCH DAMAGE.

*/

/*

• Easing Functions - inspired from http://gizma.com/easing/
• only considering the t value for the range [0, 1] => [0, 1]
  /
  EasingFunctions = {
  // no easing, no acceleration
  linear: function (t) { return t },
  // accelerating from zero velocity
  easeInQuad: function (t) { return tt },
  // decelerating to zero velocity
  easeOutQuad: function (t) { return t(2-t) },
  // acceleration until halfway, then deceleration
  easeInOutQuad: function (t) { return t<.5 ? 2tt : -1+(4-2t)t },
  // accelerating from zero velocity
  easeInCubic: function (t) { return ttt },
  // decelerating to zero velocity
  easeOutCubic: function (t) { return (--t)tt+1 },
  // acceleration until halfway, then deceleration
  easeInOutCubic: function (t) { return t<.5 ? 4ttt : (t-1)(2t-2)(2t-2)+1 },
  // accelerating from zero velocity
  easeInQuart: function (t) { return tttt },
  // decelerating to zero velocity
  easeOutQuart: function (t) { return 1-(--t)ttt },
  // acceleration until halfway, then deceleration
  easeInOutQuart: function (t) { return t<.5 ? 8tttt : 1-8(--t)ttt },
  // accelerating from zero velocity
  easeInQuint: function (t) { return ttttt },
  // decelerating to zero velocity
  easeOutQuint: function (t) { return 1+(--t)tttt },
  // acceleration until halfway, then deceleration
  easeInOutQuint: function (t) { return t<.5 ? 16ttttt : 1+16(--t)tttt }
  }

https://github.com/gre/bezier-easing