Robert Penner

/*
*
* 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. 
*
*/

function linearEase(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * currentIteration / totalIterations + startValue;
}


function easeInQuad(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * (currentIteration /= totalIterations) * currentIteration + startValue;
}


function easeOutQuad(currentIteration, startValue, changeInValue, totalIterations) {
    return -changeInValue * (currentIteration /= totalIterations) * (currentIteration - 2) + startValue;
}


function easeInOutQuad(currentIteration, startValue, changeInValue, totalIterations) {
    if ((currentIteration /= totalIterations / 2) < 1) {
        return changeInValue / 2 * currentIteration * currentIteration + startValue;
    }
    return -changeInValue / 2 * ((--currentIteration) * (currentIteration - 2) - 1) + startValue;
}


function easeInCubic(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * Math.pow(currentIteration / totalIterations, 3) + startValue;
}


function easeOutCubic(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * (Math.pow(currentIteration / totalIterations - 1, 3) + 1) + startValue;
}


function easeInOutCubic(currentIteration, startValue, changeInValue, totalIterations) {
    if ((currentIteration /= totalIterations / 2) < 1) {
        return changeInValue / 2 * Math.pow(currentIteration, 3) + startValue;
    }
    return changeInValue / 2 * (Math.pow(currentIteration - 2, 3) + 2) + startValue;
}


function easeInQuart(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * Math.pow(currentIteration / totalIterations, 4) + startValue;
}


function easeOutQuart(currentIteration, startValue, changeInValue, totalIterations) {
    return -changeInValue * (Math.pow(currentIteration / totalIterations - 1, 4) - 1) + startValue;
}


function easeInOutQuart(currentIteration, startValue, changeInValue, totalIterations) {
    if ((currentIteration /= totalIterations / 2) < 1) {
        return changeInValue / 2 * Math.pow(currentIteration, 4) + startValue;
    }
    return -changeInValue / 2 * (Math.pow(currentIteration - 2, 4) - 2) + startValue;
}


function easeInQuint(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * Math.pow(currentIteration / totalIterations, 5) + startValue;
}


function easeOutQuint(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * (Math.pow(currentIteration / totalIterations - 1, 5) + 1) + startValue;
}


function easeInOutQuint(currentIteration, startValue, changeInValue, totalIterations) {
    if ((currentIteration /= totalIterations / 2) < 1) {
        return changeInValue / 2 * Math.pow(currentIteration, 5) + startValue;
    }
    return changeInValue / 2 * (Math.pow(currentIteration - 2, 5) + 2) + startValue;
}


function easeInSine(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * (1 - Math.cos(currentIteration / totalIterations * (Math.PI / 2))) + startValue;
}


function easeOutSine(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * Math.sin(currentIteration / totalIterations * (Math.PI / 2)) + startValue;
}


function easeInOutSine(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue / 2 * (1 - Math.cos(Math.PI * currentIteration / totalIterations)) + startValue;
}


function easeInExpo(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * Math.pow(2, 10 * (currentIteration / totalIterations - 1)) + startValue;
}


function easeOutExpo(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * (-Math.pow(2, -10 * currentIteration / totalIterations) + 1) + startValue;
}


function easeInOutExpo(currentIteration, startValue, changeInValue, totalIterations) {
    if ((currentIteration /= totalIterations / 2) < 1) {
        return changeInValue / 2 * Math.pow(2, 10 * (currentIteration - 1)) + startValue;
    }
    return changeInValue / 2 * (-Math.pow(2, -10 * --currentIteration) + 2) + startValue;
}


function easeInCirc(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * (1 - Math.sqrt(1 - (currentIteration /= totalIterations) * currentIteration)) + startValue;
}


function easeOutCirc(currentIteration, startValue, changeInValue, totalIterations) {
    return changeInValue * Math.sqrt(1 - (currentIteration = currentIteration / totalIterations - 1) * currentIteration) + startValue;
}


function easeInOutCirc(currentIteration, startValue, changeInValue, totalIterations) {
    if ((currentIteration /= totalIterations / 2) < 1) {
        return changeInValue / 2 * (1 - Math.sqrt(1 - currentIteration * currentIteration)) + startValue;
    }
    return changeInValue / 2 * (Math.sqrt(1 - (currentIteration -= 2) * currentIteration) + 1) + startValue;
}