easing, tween

easing.js

/**
* easing
* @param t current time
* @parm d duartion (total time)
* @return 0 - 1
*/

/*
  weeker
Sine
Quad
Cubic
Quart
Quint
Expo
  stronger
*/

/* ------------------------------------
  easeOut
------------------------------------*/

// http://upshots.org/actionscript/jsas-understanding-easing
function easeOut(t, d) {
  return 1 - Math.pow(1 - (t / d), 4);
}


function easeOutQuart(t, d){
  return - ((t = t / d - 1) * t * t * t - 1);
}


/* ------------------------------------
  easeInOut
------------------------------------*/

function easeInOutQuint(t, d) {
  var ts=(t/=d)*t;
  var tc=ts*t;
  return (6*tc*ts + -15*ts*ts + 10*tc);
}


function easeInOutQuart(t, d) {
  var ts = t/d * 2;
  return (ts < 1 ? Math.pow(ts,4) : -((ts-=2) * Math.pow(ts,3) - 2)) * 1/2;
}


function easeInOutExpo(t, d) {
  if (!t) {return 0;}
  if (t===d) {return 1;}
  var ts =t/d*2;
  if (ts < 1) {
    return Math.pow(2,10* (ts-1)) *1/2;
  } else {
    return (-Math.pow(2, -10*--ts) + 2) *1/2;
  }
}