is in start point + duration
yoyo
when reversed progress of 1 should be 0
is in start point + delay
reset isFirstUpdateBackward flag if progress went further the end time
Method parseEasing
Method to parse easing
Parameters:
{String, Function, Array}
Returns a Function
Method splitEasing
Method to parse easing name string
Parameters:
easing
must be a String.Returns an Array
in the first repeat or without any repeats