_js-snippet-PointOnCubicBezier - Plug in the final transition time and final transition property value and it will tell you what the values are along the curve, this snippet is using the ease coordinates of cubic-bezier(.25,.1,.25,1). Cubic bezier javascript functions from: http://13thparallel.com/archive/bezier-curves/

_js-snippet-PointOnCubicBezier.js

var coord = function (x,y) {
  if(!x) var x=0;
  if(!y) var y=0;
  return {x: x, y: y};
}

function B1(t) { return t*t*t }
function B2(t) { return 3*t*t*(1-t) }
function B3(t) { return 3*t*(1-t)*(1-t) }
function B4(t) { return (1-t)*(1-t)*(1-t) }

function getBezier(percent,C1,C2,C3,C4) {
  var pos = new coord();
  pos.x = C1.x*B1(percent) + C2.x*B2(percent) + C3.x*B3(percent) + C4.x*B4(percent);
  pos.y = C1.y*B1(percent) + C2.y*B2(percent) + C3.y*B3(percent) + C4.y*B4(percent);
  return pos;
}

var finalHeight = 300;
var finalTime = 250;
var me = Services.ww.activeWindow;

var ease = { //cubic-bezier(0.25, 0.1, 0.25, 1.0)
  xs: [0, .25, .25, 1],
  ys: [0, .1, 1, 1]
};


var theBezier = ease;
me.alert(getBezier(.8, new coord(theBezier.xs[3]*finalTime,theBezier.ys[3]*finalHeight), new coord(theBezier.xs[2]*finalTime,theBezier.ys[2]*finalHeight), new coord(theBezier.xs[1]*finalTime,theBezier.ys[1]*finalHeight), new coord(theBezier.xs[0]*finalTime,theBezier.ys[0]*finalHeight)).toSource());
me.alert(getBezier(.8, new coord(theBezier.xs[0]*finalTime,theBezier.ys[0]*finalHeight), new coord(theBezier.xs[1]*finalTime,theBezier.ys[1]*finalHeight), new coord(theBezier.xs[2]*finalTime,theBezier.ys[2]*finalHeight), new coord(theBezier.xs[3]*finalTime,theBezier.ys[3]*finalHeight)).toSource());

README

Rev1

• Copy pasted
• Using 50% and using ease

Rev2

• Made it more clear what cubic bezier function I'm using