nixfilter/utils.coffee

Simplify the development of (UNIX) "Filters"

'use strict'

# Creates and returns mixin function (<object>, <mixin_objects...>) -> that mixins all properties for which <key_filter_function>(<key>, <mixin_object>, <object>) returns true into <object>
mixin_factory = (key_filter_function) ->
	(object, mixin_objects...) ->
		for mixin_object in mixin_objects
			if mixin_object
				for key of mixin_object
					if key_filter_function(key, mixin_object, object)
						object[key] = mixin_object[key]
		object

# (<object>, <mixin_objects...>) -> Mixin all OWN properties of <mixin_objects...> into <object>
mixin_own = mixin_factory (key, mixin_object) ->
	mixin_object.hasOwnProperty(key)

extend = (parent, properties, static_properties) ->
	child = (if properties?.hasOwnProperty('constructor') then properties.constructor else (-> parent.apply(@, arguments)))
	child.prototype = Object.create(parent.prototype)
	mixin_own(child.prototype, properties)
	child.prototype.constructor = child
	mixin_own(child, parent, static_properties)

# Returns true if the passed argument <value> is neither null nor undefined
is_valid_value = (value) ->
	((value isnt undefined) and (value isnt null))

# Returns the first value in <values...> that is neither null nor undefined
first_valid_value = (values...) ->
	for value in values
		if is_valid_value(value)
			return value
	return

# What this module exports
module.exports =
	extend: extend
	first_valid_value: first_valid_value
	mixin_own: mixin_own