app.coffee -------------------------------------------

{VariableTestLayer} = require "VariableTestLayer"
myVarLayer = new VariableTestLayer
    myVar: "external value"

VariableTestLayer.coffee -----------------------------

class exports.VariableTestLayer extends Layer
    constructor: (@options={}) ->
        @options.myVar ?= "internal value"
        super @options

        print @options.myVar