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- # figgy-pudding [![npm version](https://img.shields.io/npm/v/figgy-pudding.svg)](https://npm.im/figgy-pudding) [![license](https://img.shields.io/npm/l/figgy-pudding.svg)](https://npm.im/figgy-pudding) [![Travis](https://img.shields.io/travis/zkat/figgy-pudding.svg)](https://travis-ci.org/zkat/figgy-pudding) [![AppVeyor](https://ci.appveyor.com/api/projects/status/github/zkat/figgy-pudding?svg=true)](https://ci.appveyor.com/project/zkat/figgy-pudding) [![Coverage Status](https://coveralls.io/repos/github/zkat/figgy-pudding/badge.svg?branch=latest)](https://coveralls.io/github/zkat/figgy-pudding?branch=latest)
-
- [`figgy-pudding`](https://github.com/zkat/figgy-pudding) is a small JavaScript
- library for managing and composing cascading options objects -- hiding what
- needs to be hidden from each layer, without having to do a lot of manual munging
- and passing of options.
-
- ### The God Object is Dead!
- ### Now Bring Us Some Figgy Pudding!
-
- ## Install
-
- `$ npm install figgy-pudding`
-
- ## Table of Contents
-
- * [Example](#example)
- * [Features](#features)
- * [API](#api)
- * [`figgyPudding(spec)`](#figgy-pudding)
- * [`PuddingFactory(values)`](#pudding-factory)
- * [`opts.get()`](#opts-get)
- * [`opts.concat()`](#opts-concat)
- * [`opts.toJSON()`](#opts-to-json)
- * [`opts.forEach()`](#opts-for-each)
- * [`opts[Symbol.iterator]()`](#opts-symbol-iterator)
- * [`opts.entries()`](#opts-entries)
- * [`opts.keys()`](#opts-keys)
- * [`opts.value()`](#opts-values)
-
- ### Example
-
- ```javascript
- // print-package.js
- const fetch = require('./fetch.js')
- const puddin = require('figgy-pudding')
-
- const PrintOpts = puddin({
- json: { default: false }
- })
-
- async function printPkg (name, opts) {
- // Expected pattern is to call this in every interface function. If `opts` is
- // not passed in, it will automatically create an (empty) object for it.
- opts = PrintOpts(opts)
- const uri = `https://registry.npmjs.com/${name}`
- const res = await fetch(uri, opts.concat({
- // Add or override any passed-in configs and pass them down.
- log: customLogger
- }))
- // The following would throw an error, because it's not in PrintOpts:
- // console.log(opts.log)
- if (opts.json) {
- return res.json()
- } else {
- return res.text()
- }
- }
-
- console.log(await printPkg('figgy', {
- // Pass in *all* configs at the toplevel, as a regular object.
- json: true,
- cache: './tmp-cache'
- }))
- ```
-
- ```javascript
- // fetch.js
- const puddin = require('figgy-pudding')
-
- const FetchOpts = puddin({
- log: { default: require('npmlog') },
- cache: {}
- })
-
- module.exports = async function (..., opts) {
- opts = FetchOpts(opts)
- }
- ```
-
- ### Features
-
- * hide options from layer that didn't ask for it
- * shared multi-layer options
- * make sure `opts` argument is available
- * transparent key access like normal keys, through a Proxy. No need for`.get()`!
- * default values
- * key aliases
- * arbitrary key filter functions
- * key/value iteration
- * serialization
- * 100% test coverage using `tap --100`
-
- ### API
-
- #### <a name="figgy-pudding"></a> `> figgyPudding({ key: { default: val } | String }, [opts]) -> PuddingFactory`
-
- Defines an Options constructor that can be used to collect only the needed
- options.
-
- An optional `default` property for specs can be used to specify default values
- if nothing was passed in.
-
- If the value for a spec is a string, it will be treated as an alias to that
- other key.
-
- ##### Example
-
- ```javascript
- const MyAppOpts = figgyPudding({
- lg: 'log',
- log: {
- default: () => require('npmlog')
- },
- cache: {}
- })
- ```
-
- #### <a name="pudding-factory"></a> `> PuddingFactory(...providers) -> FiggyPudding{}`
-
- Instantiates an options object defined by `figgyPudding()`, which uses
- `providers`, in order, to find requested properties.
-
- Each provider can be either a plain object, a `Map`-like object (that is, one
- with a `.get()` method) or another figgyPudding `Opts` object.
-
- When nesting `Opts` objects, their properties will not become available to the
- new object, but any further nested `Opts` that reference that property _will_ be
- able to read from their grandparent, as long as they define that key. Default
- values for nested `Opts` parents will be used, if found.
-
- ##### Example
-
- ```javascript
- const ReqOpts = figgyPudding({
- follow: {}
- })
-
- const opts = ReqOpts({
- follow: true,
- log: require('npmlog')
- })
-
- opts.follow // => true
- opts.log // => Error: ReqOpts does not define `log`
-
- const MoreOpts = figgyPudding({
- log: {}
- })
- MoreOpts(opts).log // => npmlog object (passed in from original plain obj)
- MoreOpts(opts).follow // => Error: MoreOpts does not define `follow`
- ```
-
- #### <a name="opts-get"></a> `> opts.get(key) -> Value`
-
- Gets a value from the options object.
-
- ##### Example
-
- ```js
- const opts = MyOpts(config)
- opts.get('foo') // value of `foo`
- opts.foo // Proxy-based access through `.get()`
- ```
-
- #### <a name="opts-concat"></a> `> opts.concat(...moreProviders) -> FiggyPudding{}`
-
- Creates a new opts object of the same type as `opts` with additional providers.
- Providers further to the right shadow providers to the left, with properties in
- the original `opts` being shadows by the new providers.
-
- ##### Example
-
- ```js
- const opts = MyOpts({x: 1})
- opts.get('x') // 1
- opts.concat({x: 2}).get('x') // 2
- opts.get('x') // 1 (original opts object left intact)
- ```
-
- #### <a name="opts-to-json"></a> `> opts.toJSON() -> Value`
-
- Converts `opts` to a plain, JSON-stringifiable JavaScript value. Used internally
- by JavaScript to get `JSON.stringify()` working.
-
- Only keys that are readable by the current pudding type will be serialized.
-
- ##### Example
-
- ```js
- const opts = MyOpts({x: 1})
- opts.toJSON() // {x: 1}
- JSON.stringify(opts) // '{"x":1}'
- ```
-
- #### <a name="opts-for-each"></a> `> opts.forEach((value, key, opts) => {}, thisArg) -> undefined`
-
- Iterates over the values of `opts`, limited to the keys readable by the current
- pudding type. `thisArg` will be used to set the `this` argument when calling the
- `fn`.
-
- ##### Example
-
- ```js
- const opts = MyOpts({x: 1, y: 2})
- opts.forEach((value, key) => console.log(key, '=', value))
- ```
-
- #### <a name="opts-entries"></a> `> opts.entries() -> Iterator<[[key, value], ...]>`
-
- Returns an iterator that iterates over the keys and values in `opts`, limited to
- the keys readable by the current pudding type. Each iteration returns an array
- of `[key, value]`.
-
- ##### Example
-
- ```js
- const opts = MyOpts({x: 1, y: 2})
- [...opts({x: 1, y: 2}).entries()] // [['x', 1], ['y', 2]]
- ```
-
- #### <a name="opts-symbol-iterator"></a> `> opts[Symbol.iterator]() -> Iterator<[[key, value], ...]>`
-
- Returns an iterator that iterates over the keys and values in `opts`, limited to
- the keys readable by the current pudding type. Each iteration returns an array
- of `[key, value]`. Makes puddings work natively with JS iteration mechanisms.
-
- ##### Example
-
- ```js
- const opts = MyOpts({x: 1, y: 2})
- [...opts({x: 1, y: 2})] // [['x', 1], ['y', 2]]
- for (let [key, value] of opts({x: 1, y: 2})) {
- console.log(key, '=', value)
- }
- ```
-
- #### <a name="opts-keys"></a> `> opts.keys() -> Iterator<[key, ...]>`
-
- Returns an iterator that iterates over the keys in `opts`, limited to the keys
- readable by the current pudding type.
-
- ##### Example
-
- ```js
- const opts = MyOpts({x: 1, y: 2})
- [...opts({x: 1, y: 2}).keys()] // ['x', 'y']
- ```
-
- #### <a name="opts-values"></a> `> opts.values() -> Iterator<[value, ...]>`
-
- Returns an iterator that iterates over the values in `opts`, limited to the keys
- readable by the current pudding type.
-
- ##### Example
- '
- ```js
- const opts = MyOpts({x: 1, y: 2})
- [...opts({x: 1, y: 2}).values()] // [1, 2]
- ```
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