packages/transducers/src/map-keys.ts
import type { Fn2, IObjectOf } from "@thi.ng/api";
import type { Transducer } from "./api.js";
import { __iter } from "./iterator.js";
import { map } from "./map.js";
/**
* Takes a `keys` object of transformation functions and returns a
* transducer which expects object values. For each input `x` then calls
* transformation functions for each key `k` in `keys`. I.e. executes
* `keys[k](x[k], x)` and reassigns result. By default creates a shallow
* copy of each `x`.
*
* @example
* ```ts
* import { mapKeys } from "@thi.ng/transducers";
*
* [...mapKeys(
* {
* a: (x) => x != null ? x * 10 : x,
* b: (x) => x != null ? x * 100: "n/a"
* },
* [{a: 1, b: 2}, {c: 3, d: 4}]
* )]
* // [ { a: 10, b: 200 }, { c: 3, d: 4, b: 'n/a', a: undefined } ]
* ```
*
* @param keys - object of transformation functions
* @param copy - if true (default), creates a shallow copy of each incoming value
*/
export function mapKeys(
keys: IObjectOf<Fn2<any, any, any>>,
copy?: boolean
): Transducer<any, any>;
export function mapKeys(
keys: IObjectOf<Fn2<any, any, any>>,
src: Iterable<any>
): IterableIterator<any>;
export function mapKeys(
keys: IObjectOf<Fn2<any, any, any>>,
copy: boolean,
src: Iterable<any>
): IterableIterator<any>;
export function mapKeys(...args: any[]): any {
const iter = __iter(mapKeys, args);
if (iter) {
return iter;
}
const keys: IObjectOf<Fn2<any, any, any>> = args[0];
const copy = args[1] !== false;
return map((x: any) => {
const res: any = copy ? Object.assign({}, x) : x;
for (let k in keys) {
res[k] = keys[k](x[k], x);
}
return res;
});
}