Note: pending imminent deprecation
This module will be deprecated once npm v7 is released. Please do not rely on it more than absolutely necessary (ie, only if you are depending on it for use with npm v6 internal dependencies).
figgy-pudding 
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
// 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'
}))
// 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
optsargument 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
> 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
const MyAppOpts = figgyPudding({
lg: 'log',
log: {
default: () => require('npmlog')
},
cache: {}
})
> 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
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`
> opts.get(key) -> Value
Gets a value from the options object.
Example
const opts = MyOpts(config)
opts.get('foo') // value of `foo`
opts.foo // Proxy-based access through `.get()`
> 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
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)
> 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
const opts = MyOpts({x: 1})
opts.toJSON() // {x: 1}
JSON.stringify(opts) // '{"x":1}'
> 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
const opts = MyOpts({x: 1, y: 2})
opts.forEach((value, key) => console.log(key, '=', value))
> 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
const opts = MyOpts({x: 1, y: 2})
[...opts({x: 1, y: 2}).entries()] // [['x', 1], ['y', 2]]
> 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
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)
}
> 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
const opts = MyOpts({x: 1, y: 2})
[...opts({x: 1, y: 2}).keys()] // ['x', 'y']
> 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
'
const opts = MyOpts({x: 1, y: 2})
[...opts({x: 1, y: 2}).values()] // [1, 2]