@klodianimeri/pipejs/src/pipes/keys.ts

Pipe functions that provide convenient and efficient ways to work with iterators.

import { Pipe } from "../pipe.js";

export function keys(): Pipe {
    return () => {
        let i: number = -1;
        return (result: IteratorResult<any>): IteratorResult<any> => {
            if (result?.done) {
                return result;
            }

            ++i;

            if (Array.isArray(result.value) && result.value.length == 2) {
                result.value = result.value[0];
            } else {
                result.value = i;
            }

            return result;
        };
    }
}