keys-of

Returns the keys/indexes at which the specified value is located in a collection.

It’s like Array.prototype.indexOf() except it works on Maps/Objects/etc. and returns all of the keys/indexes, not just the first one.

Installation

Requires Node.js 8.3.0 or above.

npm i keys-of

API

The module exports a keysOf() function that has one other function attached to it as a method: keysOf.any().

keysOf()

Parameters

1. Bindable: c (Array, Iterator, Object, Map, Set, string, or Typed Array)
2. valueToFind (any): The value whose corresponding keys or indexes you want to locate.
3. Optional: Object argument:
   • arrays / maps / sets (arrays of classes/strings): Arrays of classes and/or string names of classes that should be treated as equivalent to Array/Map/Set (respectively).
   • compareAs (function): A callback that accepts a single existing value from the collection and transforms it before it is compared.
   • compareBy (any): If set, each existing value in the collection is assumed to be a subcollection, and the value in each subcollection corresponding to the compareBy key will be compared to valueToFind. Only applies if compareAs is not set. If compareBy is an array, it is assumed to be a chain of nested keys.
   • compareByOptions (object): An options argument for the kget module, which is used when compareBy is set.
   • inObj (boolean): Whether or not to search inherited properties if c is an Object (i.e. not another recognized type). Defaults to false.
   • loose (boolean): Whether or not to identify values loosely (as defined by looselyEquals). Defaults to false.
   • looselyEquals (function): A callback that accepts two values and returns true if they are to be considered equivalent or false otherwise. This argument is only used if loose is true. If omitted, the default behavior will, among other things, consider arrays/objects to be equal if they have the same entries.
   • reflectObj (boolean): Whether or not to use reflection to search non-enumerable Object property values. Only takes effect if c is an Object (i.e. not another recognized type). Defaults to false.

Return Value

An array of keys or numeric indexes (depending on the collection type).

Example

const keysOf = require('keys-of')

const obj = {
  a: 1,
  b: 2,
  c: 2,
  d: {},
  e: {},
}

keysOf(obj, 1) // ['a']
keysOf(obj, 2) // ['b', 'c']

keysOf(obj, {}) // []
keysOf(obj, {}, {loose: true}) // ['d', 'e']

keysOf.any()

Use this function to find the keys that correspond to any of the given values. The signature is the same as the main function except that the second parameter is called valuesToFind and takes an iterable (such as an array or string).

Example

const keysOf = require('keys-of')

const obj = {
  a: 1,
  b: 2,
  c: 2,
  d: {},
  e: {},
}

keysOf.any(obj, [1, 2]) // ['a', 'b', 'c']
keysOf.any(obj, [1, {}], {loose: true}) // ['a', 'd', 'e']

Related

• key-of: Same as this module, except it only returns the first key or index.