kset

Uses one or more keys to locate and set a value 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 kset

API

The module exports an set() function that has one other function attached to it as a method: set.all().

set()

Parameters

1. Bindable: collection (Array, Map, Object, Set, Typed Array, or WeakMap): The key-value collection with the value to be set.
2. keychain (any, or array of any): The key at which to set value, or an array of nested keys. If the key or key chain does not exist, it will be created.
3. value (any): The new value.
4. 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).
   • construct (function or false): A callback which constructs a new collection in the process of generating a nested key chain that does not already exist. The function is passed a zero-based numeric index indicating the level of nesting, and is expected to return a new collection object. To disable keychain construction altogether, set this to false.
   • elseReturn (any): A value to return in the event that the set operation was unsuccessful. Only takes effect if no elseThrow is specified. Defaults to undefined.
   • elseThrow (Error or string): An error to be thrown in the event that the set operation was unsuccessful. A string will be wrapped in an Error object automatically.
   • getType (function): A callback which specifies the type of collection to be created in the process of generating a nested key chain that does not already exist. This callback is only used if construct is not set. The function is passed a zero-based numeric index indicating the level of nesting and is expected to return a class (Object, Array, Map, etc.) or the string name of a class ('Object', 'Array', 'Map', etc.). If getType is not specified, the types argument will be used if present.
   • 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).
   • 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.
   • overwriteAncestors (boolean): Whether or not to delete non-objects if necessary to resolve the keychain. If set to false, then the module will throw an error if keychain references a non-collection. Only applies if elseThrow is not set. Defaults to false.
   • overwrite (boolean): Whether or not to allow an existing value to be replaced with value. Defaults to true.
   • preferStrict (boolean): Only applies if loose is true. If true, then strictly-identical keys will be preferred over loosely-equivalent keys. Otherwise, the first loosely-equivalent key found will be used, even if a strictly-identical one comes later. Defaults to false.
   • reverse (boolean): Set to true to use the last matching key instead of the first one. Only applies if loose is true. Defaults to false.
   • set (function): A callback which, if provided, will override the built-in code that sets the value of an individual key in 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 new value, the options object, and a callback for the built-in set behavior (to which your custom set callback can defer if it determines that it doesn’t need to override the default behavior after all).
   • type or types (function, string, or array of functions/strings): A class, or its string name, that should be used to construct new collections if a nested key chain does not already exist. To specify different collection types for each level of nesting, put the types into an array. The types argument is used only if construct and getType are not specified. If neither argument is specified, newly-created nested collections will be of the same type as collection.

Return Values

• If no changes took place, returns elseReturn if set, otherwise undefined.
• If setting the value was successful, returns the new value.

Examples

Arrays

const set = require('kset')

const arr = ['a', 'b', 'c']
set(arr, 0, 'A') // 'A'
arr // ['A', 'b', 'c']

Maps

const set = require('kset')

const map = new Map([['key', 'old']])
set(map, 'key', 'new') // 'new'
map.get('key') // 'new'

const nestedMap = new Map()
set(nestedMap, ['key1', 'key2'], 'value') // 'value'
nestedMap.get('key1').get('key2') // 'value'

Objects

const set = require('kset')

const obj = {key1: {}}
set(obj, ['key1', 'key2'], 'value') // 'value'
obj.key1.key2 // 'value'

set.all()

Use this method if you want to set multiple keys to the same value at once.

Parameters

The parameters are the same as the main function, except that the second parameter is called keychains and accepts an array of keychain arguments.

Return Value

An array of new values corresponding to the array of keychains. Each element will be the new value if it was set, otherwise elseReturn or undefined.

Example

const set = require('kset')

const obj = {a: 1, b: 2, c: 3}
set.all(obj, ['a', 'b'], 0) // [0, 0]

obj.a // 0
obj.b // 0
obj.c // 3

Related

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

• khas
• kget
• kedit
• kinc
• kdel

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

• vhas
• vget
• vsize
• vadd
• vdel