khas

Checks for the existence of one or more keys in a Map, Object, or other collection. Supports nesting, loose key matching, and more.

Installation

Requires Node.js 8.3.0 or above.

npm i khas

API

The module exports a function (has()) that has other functions attached to it as methods (e.g. has.any()).

has()

Parameters

1. Bindable: collection (Array, iterator, Map, Object, Set, string, Typed Array, or WeakMap): The key-value collection from which to retrieve a value.
2. keychain (any, or array of any): A key to check, or an array of nested keys.
3. Optional: Object argument:
   • arrays / maps / sets / weakMaps (arrays of classes/strings): Arrays of classes and/or string names of classes that should be treated as equivalent to Array/Map/Set/WeakMap (respectively).
   • get (function): A callback which, if provided, will override the built-in code that fetches an individual key from a collection. Use this if you need to support collections whose custom APIs preclude the use of parameters like maps. The callback will be called with five arguments: the collection, the key, the options object, the fallback to return if the key is not found, and a callback for the built-in get behavior (to which your custom get callback can defer if it determines that it doesn’t need to override the default behavior after all).
   • inObj (boolean): Whether or not to search inherited properties if collection is an Object (i.e. not another recognized type). Defaults to false.
   • loose (boolean): Whether or not to evaluate keys 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.

Return Value

Returns true if a value exists at the location indicated by keychain, otherwise false.

Example

const has = require('khas')

const map = new Map()
map.set('mapKey', {objKey: 'string'})

has(map, ['mapKey', 'objKey']) // true

has.any()

Has the same signature as the main function, except that the second parameter is called keychains and expects an array of keys or keychain arrays. Returns true if at least one of them points to a value, otherwise false.

Example

const has = require('khas')

has.any({c: 3, d: 4}, [['a', 'subkey'], 'b', 'c']) // true

The function tries the keys a.subkey, b, and c in that order. Since there is a value located at c, the function returns true.

has.in()

This method is an alias for calling the main has() method with the inObj option set to true.

has.any.in()

This method is an alias for calling has.any() with the inObj option set to true.

Related

The “k” family of modules works on keyed/indexed collections.

• kget
• kedit
• kset
• kinc
• kdel

The “v” family of modules works on any collection of values.

• vhas
• vget
• vsize
• vadd
• vdel