map

Transforms the values and/or keys of a plain object in a single pass.

Both callbacks are optional and default to identity (no transformation). When mapValue is omitted the original values are preserved; when mapKey is omitted the original keys are preserved.

Note: if two different keys map to the same output key the last one wins (insertion order). Entries whose mapped key is a prototype-polluting string (__proto__, constructor, prototype) are silently skipped.

Available since v2.0.0

Import

import { map } from '@helpers4/object';

Signature

map<TObj extends Record<string, unknown>, TVal = indexedAccess, TKey extends PropertyKey = keyof TObj>(obj: TObj | null | undefined, mapValue?: function, mapKey?: function): Record<TKey, TVal>

Parameters

Parameter	Type	Description
obj	TObj | null | undefined	The source object
mapValue	function	Callback called with (value, key) for each entry. Defaults to identity. (optional)
mapKey	function	Callback called with (key, value) for each entry. Defaults to identity. (optional)

Returns

Record<TKey, TVal> — A new object with transformed keys and/or values

Examples

Transform values

Maps each value of an object through a transform function.

map({ a: 1, b: 2 }, v => v * 10)
// => { a: 10, b: 20 }

Transform keys

Maps each key of an object through a transform function.

map({ a: 1, b: 2 }, undefined, k => k.toUpperCase())
// => { A: 1, B: 2 }

Transform both keys and values in a single pass

Provide both a value mapper and a key mapper to rewrite the whole object.

map(
  { price: 100, discount: 20 },
  v => v / 100,
  k => `${k}Ratio`
)
// => { priceRatio: 1, discountRatio: 0.2 }

Source

View source on GitHub