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September 9, 2014 17:40
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define object properties in coffeescript
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| with_defaults = (object, defaults) -> | |
| f = (previous, current) -> | |
| unless Object.hasOwnProperty(previous, current) | |
| previous[current] = object[current] | |
| previous | |
| Object.keys(object).reduce f, defaults | |
| # "Fancy" version of Object.defineProperty that stores and applies a given | |
| # default value | |
| define_uncurried = (object, name, descriptor) -> | |
| # A default value for accessors might be added, however it has to be removed | |
| # from the descriptor before calling Object.defineProperty. | |
| # According to the Mozilla documentation of defineProperty, accessor | |
| # descriptors may not have a default value. | |
| # | |
| # https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/defineProperty | |
| if descriptor.is_accessor? | |
| value = descriptor.value | |
| delete descriptor.value | |
| Object.defineProperty object, name, descriptor | |
| # Apply default value | |
| object[name] = value if descriptor.is_accessor? | |
| module.exports = | |
| define: (object, name, descriptor) -> | |
| # Return a partially applied function when only the object is given | |
| # | |
| # This enables usage as such: | |
| # | |
| # P = require './define' | |
| # {ReadOnly, Data, Descriptor} = P | |
| # | |
| # o = {} | |
| # | |
| # define = P.define o | |
| # | |
| # define 'readonly', ReadOnly Data Descriptor value: 10 | |
| # define 'writable', Data Descriptor value: 20 | |
| # | |
| return (n, d) -> define_uncurried object, n, d if 1 == arguments.length | |
| return define_uncurried object, name, descriptor if 3 == arguments.length | |
| throw new Error 'Wrong number of arguments given. Only one or three arguments allowed.' | |
| # Returns a descriptor holding the given getter and/or setter functions, as | |
| # well as a boolean property `is_accessor` set to true. | |
| # | |
| # Descriptor -> Descriptor | |
| # Function -> Descriptor | |
| # Descriptor, Function -> Descriptor | |
| # Descriptor, Function, Function -> Descriptor | |
| # undefined, null -> Descriptor | |
| Accessor: (args...) -> | |
| options = { is_accessor: true } | |
| return options unless args.length | |
| options = with_defaults args[0], options if T.is_object args[0] | |
| options.get = do args.shift if T.is_function args[0] | |
| options.set = do args.shift if T.is_function args[0] | |
| options | |
| Descriptor: (options = {}) -> | |
| with_defaults options, | |
| configurable: true | |
| enumerable: false | |
| Data: (options = {}) -> | |
| with_defaults options, | |
| writable: true | |
| is_data: true | |
| ReadOnly: (options = {}) -> | |
| if options.is_accessor? | |
| console.log 'WARNING: ReadOnly is only applicable to data descriptors, given: ', options | |
| with_defaults options, | |
| writable: false | |
| value: null | |
| is_data: true | |
| Enumerable: (options = {}) -> | |
| with_defaults options, enumerable: true |
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