Tweener Coffescript Class

tweener.coffee

###
An utility object which allows to create different animations with different keyframes.
The get_value method return the interpolated value of the selected animation depending on time parameter.
###

class Tweener

  constructor: ->
		@keyframes = new Object()

	add_keyframe: ( name, data, reset = false ) ->

		if reset
			@keyframes[name] = []
		else
			@keyframes[name] ?= []

		unless data.hasOwnProperty('ease')
			data.ease = 'linearNone'

		@keyframes[name].push data

	get_value: (name, time) ->
		return unless @keyframes[name]?

		@data = @keyframes[name]

		index_key_1 = @get_ending_keyframe time
		index_key_0 = index_key_1 - 1	
		key_1 = @data[index_key_1]
		key_0 = @data[index_key_0]

		max_time = key_1.time - key_0.time
		the_time = time - key_0.time
		max_value = key_1.value - key_0.value

		x = Easie[ key_0.ease ]( the_time, key_0.value, max_value, max_time )
		#x = max_value * the_time / max_time + key_0.value
		
		return x

	get_ending_keyframe: (time) ->
		l = @data.length
		for index in [ 1 ... (l - 1) ]
			if @data[index].time >= time
				return index
		return l - 1

usage.coffee

# Note: You need to import Easie.coffee (https://github.com/jimjeffers/Easie)
  
# Create the object
@tweener = new Tweener()

# Adding some animations with their different keyframes
@tweener.add_keyframe('my_animation', { time: 0, value: 20, ease:'quadIn'})
@tweener.add_keyframe('my_animation', { time: 0.3, value: 50, ease:'quadIn'})
@tweener.add_keyframe('my_animation', { time: 0.6, value: 100, ease:'quadIn'})
@tweener.add_keyframe('my_animation', { time: 1, value: 80, ease:'quadIn'})

@tweener.add_keyframe('other_animation', { time: 0, value: 50})
@tweener.add_keyframe('other_animation', { time: 1, value: 10})


# Get the interpolate value passing the aniamtion name and the time as a paramenters

interpolated_value = @tweener.get_value 'my_animation', 0.8

other_interpolated_value = @tweener.get_value 'other_animation', 0.5