mapKeys (for Maps)
Creates a new Map with the same values but with keys transformed by the provided function.
typescript
const transformed = mapKeys(map, getNewKey);INFO
This function is available exclusively from es-toolkit/map to avoid potential conflicts with similar functions for other collection types.
Usage
mapKeys(map, getNewKey)
Use mapKeys when you want to transform the keys of a Map while keeping the values unchanged. Provide a function that generates a new key from each entry, and it returns a new Map with the transformed keys.
typescript
import { mapKeys } from 'es-toolkit/map';
const map = new Map([
['a', 1],
['b', 2],
['c', 3],
]);
const result = mapKeys(map, (value, key) => key.toUpperCase());
// Result:
// Map(3) {
// 'A' => 1,
// 'B' => 2,
// 'C' => 3
// }You can transform keys in various ways.
typescript
import { mapKeys } from 'es-toolkit/map';
// Add prefix to keys
const categories = new Map([
['fruit', ['apple', 'banana']],
['vegetable', ['carrot', 'potato']],
]);
const prefixed = mapKeys(categories, (value, key) => `category_${key}`);
// Result: Map with keys 'category_fruit', 'category_vegetable'
// Transform based on value
const scores = new Map([
['alice', 95],
['bob', 87],
['charlie', 92],
]);
const ranked = mapKeys(scores, (value, key) => (value >= 90 ? `top_${key}` : key));
// Result: Map with keys 'top_alice', 'bob', 'top_charlie'Parameters
map(Map<K, V>): The Map to transform.getNewKey((value: V, key: K, object: Map<K, V>) => K): A function that generates a new key from a value-key pair.
Returns
(Map<K, V>): A new Map with transformed keys and the same values.