A collection of Easing functions

easing.js

/**
 * Port of Penner Easing Equations into human legible dot-notation syntax.
 *
 * @author Robert Penner / http://robertpenner.com/easing/
 * @author jonobr1 / http://jonobr1.com/
 *
 * License: http://robertpenner.com/easing_terms_of_use.html
 *
 */
(function() {

  var root = this;
  var previousEasing = root.Easing || {};
  
  var Easing = root.Easing = {

    noConflict: function() {
      root.Easing = previousEasing;
      return Easing;
    },

    setDefault: function(func) {
      Easing.defaultEasing = func;
      return Easing;
    },

    /**
     * t: Current Time
     * b: Start Value
     * c: End Value
     * d: Duration
     */

    swing: function (t, b, c, d) {
      return Easing[Easing.defaultEasing](t, b, c, d);
    },

    Quadratic: {
      In: function (t, b, c, d) {
        return c * (t /= d) * t + b;
      },
      Out: function(t, b, c, d) {
        return -c * (t /= d) * (t - 2) + b;
      },
      InOut: 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: {
      In: function (t, b, c, d) {
        return c * (t /= d) * t * t + b;
      },
      Out: function (t, b, c, d) {
        return c * ((t = t / d - 1) * t * t + 1) + b;
      },
      InOut: 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;
      }
    },
    Quartic: {
      In: function (t, b, c, d) {
        return c * (t /= d) * t * t * t + b;
      },
      Out: function (t, b, c, d) {
        return - c * ((t = t / d - 1) * t * t * t - 1) + b;
      },
      InOut: 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;
      }
    },
    Quintic: {
      In: function (t, b, c, d) {
        return c * (t /=d ) * t * t * t * t + b;
      },
      Out: function (t, b, c, d) {
        return c * ((t = t / d - 1) * t * t * t * t + 1) + b;
      },
      InOut: 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: {
      In: function (t, b, c, d) {
        return - c * Math.cos(t / d * (Math.PI / 2)) + c + b;
      },
      Out: function (t, b, c, d) {
        return c * Math.sin(t / d * (Math.PI / 2)) + b;
      },
      InOut: function (t, b, c, d) {
        return - c / 2 * (Math.cos(Math.PI * t / d) - 1) + b;
      }
    },
    Exponential: {
      In: function (t, b, c, d) {
        return (t == 0) ? b : c * Math.pow(2, 10 * (t / d - 1)) + b;
      },
      Out: function (t, b, c, d) {
        return (t == d) ? b + c : c * ( - Math.pow(2, - 10 * t / d) + 1) + b;
      },
      InOut: 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;
      }
    },
    Circular: {
      In: function (t, b, c, d) {
        return - c * (Math.sqrt(1 - (t /= d) * t) - 1) + b;
      },
      Out: function (t, b, c, d) {
        return c * Math.sqrt(1 - (t = t / d - 1) * t) + b;
      },
      InOut: 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: {
      In: function (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 * 0.3;
        if (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 -= 1)) * Math.sin((t * d - s) * (2 * Math.PI) / p)) + b;
      },
      Out: function (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 * 0.3;
        if (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;
      },
      InOut: function (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 * (0.3 * 1.5);
        if (a < Math.abs(c)) {
          a = c;
          s = p / 4;
        } else {
          s = p / (2 * Math.PI) * Math.asin(c / a);
        }
        if (t < 1) return - 0.5 * (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 ) * 0.5 + c + b;
      }
    },
    Back: {
      In: function (t, b, c, d, s) {
        if (s == undefined) s = 1.70158;
        return c * (t /= d) * t * ((s + 1) * t - s) + b;
      },
      Out: function (t, b, c, d, s) {
        if (s == undefined) s = 1.70158;
        return c * ((t = t / d - 1) * t * ((s + 1) * t + s) + 1) + b;
      },
      InOut: function (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;
      }
    },
    Bounce: {
      In: function (t, b, c, d) {
        return c - Easing.OutBounce(d - t, 0, c, d) + b;
      },
      Out: 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 + 0.75) + b;
        } else if (t < (2.5 / 2.75)) {
          return c * (7.5625 * (t-=(2.25 / 2.75)) * t + 0.9375) + b;
        } else {
          return c * (7.5625 * (t -= (2.625 / 2.75)) * t + 0.984375) + b;
        }
      },
      InOut: function (t, b, c, d) {
        if (t < d / 2) return Easing.InBounce(t * 2, 0, c, d) * 0.5 + b;
        return Easing.OutBounce(t * 2 - d, 0, c, d) * 0.5 + c * 0.5 + b;
      }
    }
  };

  Easing.setDefault(Easing.Quadratic.Out);

})();