get-wild


- NAME
- FEATURES
- INSTALLATION
- SYNOPSIS
- Negative array indices
- Wildcards
- DESCRIPTION
- Why?
- Why not?
- TYPES
- EXPORTS
- get-wild
- get
- getter
- split
- get-wild/fp
- get
- getter
- OPTIONS
- collect
- default
- flatMap
- map
- split
- DEVELOPMENT
- COMPATIBILITY
- SEE ALSO
- VERSION
- AUTHOR
- COPYRIGHT AND LICENSE

NAME

get-wild - extract nested properties from an object with support for wildcards

FEATURES

- configurable wildcard support, e.g. "foo.*.bar"
- support for negative array indices, e.g. "foo[-1].bar"
- pluggable path parser
- no dependencies
- < 800 B minified + gzipped
- curried (data last) versions for functional programming
- fully typed (TypeScript)
- CDN builds (UMD) - [jsDelivr][], [unpkg][]

INSTALLATION

``
$ npm install get-wild
`

SYNOPSIS

`javascript
import { get } from 'get-wild'

const obj = { foo: { bar: { baz: 'quux' } } }

get(obj, 'foo.bar.baz') // "quux"
get(obj, 'foo.fizz.buzz') // undefined
get(obj, 'foo.fizz.buzz', 42) // 42
get(obj, ['foo', 'bar', 'baz']) // "quux"
get(obj, ['foo', 'fizz', 'buzz'], 42) // 42
`

$3

`javascript
const array = [
[{ value: 1 }, { value: 2 }, { value: 3 }],
[{ value: 4 }, { value: 5 }, { value: 6 }],
[{ value: 7 }, { value: 8 }, { value: 9 }],
]

get(array, '[1][-2].value') // 5
get(array, [-1, -1, 'value']) // 9
`

$3

`javascript
const data = {
users: {
'abc123': {
name: 'John Doe',
homepage: 'https://example.com/john-doe',
hobbies: ['eating', 'sleeping'],
},
'def345': {
name: 'Jane Doe',
homepage: 'https://example.com/jane-doe',
},
'ghi567': {
name: 'Nemo',
hobbies: ['singing', 'dancing'],
},
}
}

get(data, 'users[0].name') // "John Doe"
get(data, 'users[-1].name') // "Nemo"
get(data, 'users.*.name') // ["John Doe", "Jane Doe", "Nemo"]

get(data, 'users.*.homepage')
// ["https://example.com/john-doe", "https://example.com/jane-doe", undefined]

// also works with arrays
get(array, '[1].*.value') // [4, 5, 6]
get(array, '[-1].*.value') // [7, 8, 9]
`


#### Flatten results

`javascript
get(data, 'users.*.hobbies')
// ["eating", "sleeping", undefined, "singing", "dancing"]
`


#### Remove missing results

`javascript
get(data, 'users.*.hobbies', [])
// ["eating", "sleeping", "singing", "dancing"]
`


#### Raw results

`javascript
get(data, 'users.**.hobbies')
// [["eating", "sleeping"], undefined, ["singing", "dancing"]]
`

DESCRIPTION

This module exports a function which can be used to extract nested properties
from an object, including arrays and any other non-falsey values. This is
similar to the get function provided by Lodash (and many other libraries),
but it adds the following features:

- wildcard support, e.g. "foo..bar..baz"
- support for negative array indices, e.g. "foo[-1][-2]"

In addition to the default get implementation, get-wild exports a
builder function (getter) which can be used to create a custom
get with different options baked in, as well as curried
(data last) versions of get and getter to
facilitate functional composition and reuse.

Why?

I needed a small, dependency-free version of [Lodash.get][Lodash.get] with wildcard
support, and preferably with an option to filter out/exclude missing values.
Although there are a huge number of get implementations on NPM, I could only
find one or two with wildcard support and none that are
standalone/dependency-free.

Why not?

If you don't need support for wildcards, negative array-indices, or other
options, there are smaller implementations, e.g.
[dlv][].

TYPES

The following types are referenced in the descriptions below.

`typescript
type Options = {
collect?: Collect;
default?: any;
flatMap?: PropertyKey | false;
map?: PropertyKey | false;
parser?: string | Parser;
split?: Options['parser'];
}

interface Collect {
(value: {}) => Array;
(value: {}, index: number) => ArrayLike;
}

type Parser = (path: string) => Array;
type Path = PropertyKey | Array;
`

EXPORTS

get-wild

$3

- Type: (obj: any, path: Path, $default?: any) => T

`javascript
import { get } from 'get-wild'

get(obj, 'foo.*.bar', [])
`

Takes an object, a path and an optional default value, and returns the
value(s) found in the object at the specified path, or the default value
(which is undefined by default) if the path doesn't exist or the value is
undefined. The path can be supplied as a dotted expression (string), symbol
or number, or an array of strings, symbols or numbers.

The syntax of dotted path expressions mostly matches that of
regular JavaScript path expressions, with a few additions.

If there are no steps in the path, the object itself is returned (or the
default value if the object is undefined).

Wildcard matching is performed by collecting an array of values
at the wildcard's location and recursively getting the remainder of
the path from each value. Wildcards can be used at any locations in a path to
turn a single lookup into an array of lookup results for values at that
location.

The values returned by wildcard matches can be customized. By default, *
flattens the results (using [flatMap][flatMap]), while ** uses
[map][map], which returns the results verbatim, though this mapping can be
configured (or disabled) via the map and flatMap
options.

The get export is generated by a builder function, getter, which
can be used to create a custom get function with different options.

$3

- Type: (options?: Options) => (obj: any, path: Path, $default?: any) => T

`javascript
import { getter } from 'get-wild'

const get = getter({ split: '/' })
const obj = { foo: { bar: { baz: 42 } } }

get(obj, 'foo/bar/baz') // 42
`

getter is a function which is used to build get functions. The default
get export is generated by calling getter with no arguments, which uses the
following default options:

`javascript
{
collect: Object.values,
default: undefined,
flatMap: '*',
map: '**',
split: defaultParser,
}
`

The behavior of get can be configured by generating a custom version which
overrides these defaults, e.g.:

`javascript
import { getter } from 'get-wild'

const split = path => path.split('/')
const get = getter({ split })

get(obj, 'foo/bar/*/quux')
`

$3

- Type: Parser
- Aliases: parse, parser

`javascript
import { getter, split } from 'get-wild'
import memoize from '@example/memoizer'

const memoized = memoize(split)
const get = getter({ split: memoized })

get(obj, '...')
`

The default function used by get to turn a path expression (string)
into an array of steps (strings, symbols or numbers).

The array is not mutated, so, e.g., the function can be memoized to avoid
re-parsing long/frequently-used paths. Alternatively, the path can be
pre-parsed into an array (this is done automatically if the
curried versions are used).



#### Syntax

The parser supports an extended version of JavaScript's native path syntax,
e.g. the path:

`javascript
a[-1].b[42].-1.42["c.d"].e['f g'].*.h["i \\"j\\" k"]['']
`

is parsed into the following steps:

`javascript
['a', -1, 'b', 42, '-1', '42', 'c.d', 'e', 'f g', '*', 'h', 'i "j" k', '']
`

Properties are either unquoted names (strings), bracketed integers, or
bracketed single or double-quoted strings. Integers can be signed (-1, +42)
or unsigned (42). Unquoted names can contain any characters apart from spaces
(\s), ", ', `, [, ], . or \.

Unquoted property names must be preceded by a dot unless the name is at the
start of the path, in which case the dot must be omitted. Bracketed values
must not be preceded by a dot.

If the path is an empty string, an empty array is returned.

get-wild/fp

$3

- Type: (path: Path, $default?: any) => (obj: any) => U

`javascript
import { get } from 'get-wild/fp'

const followers = get('followers.*.name', [])

followers(user) // get(user, ["followers", "*", "name"], [])

const allFollowers = users.flatMap(followers)
`

A curried version of get which takes a path and an optional default
value and returns a function which takes an object and returns the value(s)
located at the path.

$3

- Type: (options?: Options) => (path: Path, $default?: any) => (obj: any) => U

`javascript
import { getter } from 'get-wild/fp'

const get = getter({ default: [], split: '.' })
const followers = get('followers.*.name')

followers(user) // get(user, ["followers", "*", "name"], [])

const allFollowers = users.flatMap(followers)
`

A variant of getter which takes an optional Options
object and returns a curried version of get with the options baked
in.

OPTIONS

collect

- Type:
- (value: {}) => Array
- (value: {}, index: number) => ArrayLike
- Default: Object.values

`javascript
import { getter } from 'get-wild'

const collect = value => {
return (value instanceof Map || value instanceof Set)
? Array.from(value.values())
: Object.values(value)
}

const map = new Map([
[1, { value: 'foo' }],
[2, { value: 'bar' }],
[3, { value: 'baz' }],
[4, { value: 'quux' }],
])

const obj = { map }
const get = getter({ collect })

get(obj, 'map[0].value') // "foo"
get(obj, 'map[-1].value') // "quux"
get(obj, 'map.*.value') // ["foo", "bar", "baz", "quux"]
`

The collect function is used to convert a non-array value matched by a
wildcard or indexed by an integer into an array of values. If not supplied, it
defaults to [Object.values][Object.values], which works with plain objects,
array-likes, and other non-nullish values. It can be overridden to add support
for traversable values which aren't plain objects or arrays, e.g. DOM elements
or ES6 Map and Set instances.

Note that the value passed to collect is not falsey and not an array, as both
are handled without calling collect.

For indexed access, the collect function is passed the index as its second
argument and the return value can be an array-like rather than a full-blown
array. For wildcard matches, the index is omitted and the return value is an
an array. This distinction can be used to customize the result, e.g. to avoid
constructing a large array if only a single value is accessed, or to customize
the order of the values.

default

- Type: any
- Default: undefined

`javascript
const get = getter({ default: [] })

get(data, 'users.*.hobbies')
// ["eating", "sleeping", "singing", "dancing"]

get(data, 'users.*.hobbies', [])
// ["eating", "sleeping", "singing", "dancing"]

get(data, 'users.*.hobbies', undefined)
// ["eating", "sleeping", undefined, "singing", "dancing"]

`

This option allows the default value to be baked into a get function. If no
third argument is passed to the function, this value is returned for
missing/undefined properties. Otherwise, the supplied value is returned.

flatMap

- Type: PropertyKey | false
- Default: "*"

`javascript
import { getter } from 'get-wild'

const get = getter({ flatMap: '*', map: '' })

get(data, 'users.**.hobbies', [])
// ["eating", "sleeping", "singing", "dancing"]

get(data, 'users.*.hobbies', [])
// [["eating", "sleeping"], [], ["singing", "dancing"]]
`

The token used to map values at the specified location and flatten the results.

If set to false, wildcard matching with flatMap is disabled and the token is
treated as a regular property name.

$3

Wildcard matching with flatMap behaves in a similar way to directory/filename
matching with [globs][] (minus the pattern matching). The selected properties
(at the end of the path) are returned as direct children of the resulting array
(wildcard matches always return an array), either as matched results or as
default values if there's no match.

For example, with the default mapping, a path such as
accounts.active..followers..name, which extracts the names of all followers
of active accounts, would return an array of account names interspersed with
default values where an account doesn't have any followers (or if a follower's
name is undefined), e.g.:

`javascript
get(data, 'accounts.active..followers..name')
// ["john", "paul", undefined, "george", undefined, "ringo"]
`

This can be reduced to just the names by setting the default value to an empty
array, e.g.:

`javascript
get(data, 'accounts.active..followers..name', [])
// ["john", "paul", "george", "ringo"]
`

$3

Note that with the default parser, the token must be a
syntactically-valid name, e.g. this doesn't work:

`javascript
import { getter } from 'get-wild'

const obj = { foo: [{ bar: 1 }, { bar: 2 }] }
const get = getter({ flatMap: '[]' })

get(obj, 'foo.[].bar') // SyntaxError: Invalid step @ 3: "foo.[].bar"
`

If a custom parser is supplied, any token can be used:

`javascript
const get = getter({ flatMap: '[]', split: '.' })

get(obj, 'foo.[].bar') // [1, 2]
`

map

- Type: PropertyKey | false
- Default: "**"

`javascript
import { getter } from 'get-wild'

const get = getter({ map: '', flatMap: '*' })

get(data, 'users.*.hobbies', [])
// [["eating", "sleeping"], [], ["singing", "dancing"]]

get(data, 'users.**.hobbies', [])
// ["eating", "sleeping", "singing", "dancing"]
`

The token used to map values at the specified location without flattening the
results.

Matching with map selects the same values as flatMap, but they remain
nested inside arrays, with each enclosing map in the path adding another
layer of wrapping.

If set to false, wildcard matching with map is disabled and the token is
treated as a regular property name.

split

- Type: string | Parser
- Default: split
- Alias: parser

`javascript
import { getter } from 'get-wild'

const split = path => path.split('.')
const get = getter({ split })
const obj = { '': { '': 42 } }

get(obj, '.') // 42
`

A function which takes a path expression (string) and parses it into an array
of property names (strings, symbols or numbers). If not supplied, a
default parser which supports an extended version of JavaScript's
native path syntax is used.

As a shortcut, if the value is a string, a function which splits the path on
that string is used, i.e. the following are equivalent:

`javascript
const split = path => path.split('.')
const get = getter({ split })
`

`javascript
const get = getter({ split: '.' })
``

DEVELOPMENT

COMPATIBILITY

- Maintained Node.js versions and compatible browsers

SEE ALSO

- @gizt/selector
- dot-wild-tiny
- jsonpath
- object-path-wild
- qim

VERSION

3.0.2

AUTHOR

chocolateboy

COPYRIGHT AND LICENSE

Copyright © 2020-2022 by chocolateboy.

This is free software; you can redistribute it and/or modify it under the terms
of the MIT license.

[dlv]: https://www.npmjs.com/package/dlv
[flat]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flat
[flatMap]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/flatMap
[globs]: https://en.wikipedia.org/wiki/Glob_(programming)
[jsDelivr]: https://cdn.jsdelivr.net/npm/get-wild
[Lodash.get]: https://www.npmjs.com/package/lodash.get
[map]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/map
[Object.values]: https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Object/values
[polyfill]: https://www.npmjs.com/package/array-flat-polyfill
[unpkg]: https://unpkg.com/get-wild