269 lines
7.5 KiB
Markdown
269 lines
7.5 KiB
Markdown
# Note: pending imminent deprecation
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**This module will be deprecated once npm v7 is released. Please do not rely
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on it more than absolutely necessary (ie, only if you are depending on
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it for use with npm v6 internal dependencies).**
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----
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# figgy-pudding [](https://npm.im/figgy-pudding) [](https://npm.im/figgy-pudding) [](https://travis-ci.org/npm/figgy-pudding) [](https://coveralls.io/github/npm/figgy-pudding?branch=latest)
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[`figgy-pudding`](https://github.com/npm/figgy-pudding) is a small JavaScript
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library for managing and composing cascading options objects -- hiding what
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needs to be hidden from each layer, without having to do a lot of manual munging
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and passing of options.
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### The God Object is Dead!
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### Now Bring Us Some Figgy Pudding!
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## Install
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`$ npm install figgy-pudding`
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## Table of Contents
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* [Example](#example)
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* [Features](#features)
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* [API](#api)
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* [`figgyPudding(spec)`](#figgy-pudding)
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* [`PuddingFactory(values)`](#pudding-factory)
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* [`opts.get()`](#opts-get)
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* [`opts.concat()`](#opts-concat)
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* [`opts.toJSON()`](#opts-to-json)
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* [`opts.forEach()`](#opts-for-each)
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* [`opts[Symbol.iterator]()`](#opts-symbol-iterator)
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* [`opts.entries()`](#opts-entries)
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* [`opts.keys()`](#opts-keys)
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* [`opts.value()`](#opts-values)
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### Example
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```javascript
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// print-package.js
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const fetch = require('./fetch.js')
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const puddin = require('figgy-pudding')
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const PrintOpts = puddin({
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json: { default: false }
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})
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async function printPkg (name, opts) {
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// Expected pattern is to call this in every interface function. If `opts` is
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// not passed in, it will automatically create an (empty) object for it.
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opts = PrintOpts(opts)
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const uri = `https://registry.npmjs.com/${name}`
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const res = await fetch(uri, opts.concat({
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// Add or override any passed-in configs and pass them down.
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log: customLogger
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}))
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// The following would throw an error, because it's not in PrintOpts:
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// console.log(opts.log)
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if (opts.json) {
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return res.json()
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} else {
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return res.text()
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}
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}
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console.log(await printPkg('figgy', {
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// Pass in *all* configs at the toplevel, as a regular object.
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json: true,
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cache: './tmp-cache'
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}))
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```
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```javascript
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// fetch.js
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const puddin = require('figgy-pudding')
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const FetchOpts = puddin({
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log: { default: require('npmlog') },
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cache: {}
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})
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module.exports = async function (..., opts) {
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opts = FetchOpts(opts)
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}
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```
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### Features
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* hide options from layer that didn't ask for it
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* shared multi-layer options
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* make sure `opts` argument is available
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* transparent key access like normal keys, through a Proxy. No need for`.get()`!
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* default values
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* key aliases
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* arbitrary key filter functions
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* key/value iteration
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* serialization
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* 100% test coverage using `tap --100`
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### API
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#### <a name="figgy-pudding"></a> `> figgyPudding({ key: { default: val } | String }, [opts]) -> PuddingFactory`
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Defines an Options constructor that can be used to collect only the needed
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options.
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An optional `default` property for specs can be used to specify default values
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if nothing was passed in.
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If the value for a spec is a string, it will be treated as an alias to that
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other key.
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##### Example
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```javascript
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const MyAppOpts = figgyPudding({
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lg: 'log',
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log: {
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default: () => require('npmlog')
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},
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cache: {}
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})
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```
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#### <a name="pudding-factory"></a> `> PuddingFactory(...providers) -> FiggyPudding{}`
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Instantiates an options object defined by `figgyPudding()`, which uses
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`providers`, in order, to find requested properties.
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Each provider can be either a plain object, a `Map`-like object (that is, one
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with a `.get()` method) or another figgyPudding `Opts` object.
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When nesting `Opts` objects, their properties will not become available to the
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new object, but any further nested `Opts` that reference that property _will_ be
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able to read from their grandparent, as long as they define that key. Default
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values for nested `Opts` parents will be used, if found.
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##### Example
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```javascript
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const ReqOpts = figgyPudding({
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follow: {}
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})
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const opts = ReqOpts({
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follow: true,
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log: require('npmlog')
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})
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opts.follow // => true
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opts.log // => Error: ReqOpts does not define `log`
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const MoreOpts = figgyPudding({
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log: {}
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})
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MoreOpts(opts).log // => npmlog object (passed in from original plain obj)
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MoreOpts(opts).follow // => Error: MoreOpts does not define `follow`
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```
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#### <a name="opts-get"></a> `> opts.get(key) -> Value`
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Gets a value from the options object.
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##### Example
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```js
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const opts = MyOpts(config)
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opts.get('foo') // value of `foo`
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opts.foo // Proxy-based access through `.get()`
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```
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#### <a name="opts-concat"></a> `> opts.concat(...moreProviders) -> FiggyPudding{}`
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Creates a new opts object of the same type as `opts` with additional providers.
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Providers further to the right shadow providers to the left, with properties in
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the original `opts` being shadows by the new providers.
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##### Example
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```js
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const opts = MyOpts({x: 1})
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opts.get('x') // 1
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opts.concat({x: 2}).get('x') // 2
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opts.get('x') // 1 (original opts object left intact)
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```
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#### <a name="opts-to-json"></a> `> opts.toJSON() -> Value`
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Converts `opts` to a plain, JSON-stringifiable JavaScript value. Used internally
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by JavaScript to get `JSON.stringify()` working.
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Only keys that are readable by the current pudding type will be serialized.
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##### Example
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```js
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const opts = MyOpts({x: 1})
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opts.toJSON() // {x: 1}
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JSON.stringify(opts) // '{"x":1}'
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```
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#### <a name="opts-for-each"></a> `> opts.forEach((value, key, opts) => {}, thisArg) -> undefined`
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Iterates over the values of `opts`, limited to the keys readable by the current
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pudding type. `thisArg` will be used to set the `this` argument when calling the
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`fn`.
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##### Example
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```js
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const opts = MyOpts({x: 1, y: 2})
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opts.forEach((value, key) => console.log(key, '=', value))
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```
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#### <a name="opts-entries"></a> `> opts.entries() -> Iterator<[[key, value], ...]>`
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Returns an iterator that iterates over the keys and values in `opts`, limited to
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the keys readable by the current pudding type. Each iteration returns an array
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of `[key, value]`.
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##### Example
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```js
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const opts = MyOpts({x: 1, y: 2})
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[...opts({x: 1, y: 2}).entries()] // [['x', 1], ['y', 2]]
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```
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#### <a name="opts-symbol-iterator"></a> `> opts[Symbol.iterator]() -> Iterator<[[key, value], ...]>`
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Returns an iterator that iterates over the keys and values in `opts`, limited to
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the keys readable by the current pudding type. Each iteration returns an array
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of `[key, value]`. Makes puddings work natively with JS iteration mechanisms.
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##### Example
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```js
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const opts = MyOpts({x: 1, y: 2})
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[...opts({x: 1, y: 2})] // [['x', 1], ['y', 2]]
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for (let [key, value] of opts({x: 1, y: 2})) {
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console.log(key, '=', value)
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}
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```
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#### <a name="opts-keys"></a> `> opts.keys() -> Iterator<[key, ...]>`
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Returns an iterator that iterates over the keys in `opts`, limited to the keys
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readable by the current pudding type.
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##### Example
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```js
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const opts = MyOpts({x: 1, y: 2})
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[...opts({x: 1, y: 2}).keys()] // ['x', 'y']
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```
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#### <a name="opts-values"></a> `> opts.values() -> Iterator<[value, ...]>`
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Returns an iterator that iterates over the values in `opts`, limited to the keys
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readable by the current pudding type.
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##### Example
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'
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```js
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const opts = MyOpts({x: 1, y: 2})
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[...opts({x: 1, y: 2}).values()] // [1, 2]
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```
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