Function foreach

Extension/src/Utility/Async/iterators.ts:11–28

(items: undefined | Iterable<T> | Promise<Iterable<T> | undefined> | Promise<undefined> | AsyncIterable<T> | Promise<AsyncIterable<T>>, predicate: (item: T) => Promise<TResult>)

/** an async foreach function to iterate over any iterable/async iterable, calling a function on each item in parallel as possible */
export async function foreach<T, TResult>(items: undefined | Iterable<T> | Promise<Iterable<T> | undefined> | Promise<undefined> | AsyncIterable<T> | Promise<AsyncIterable<T>>, predicate: (item: T) => Promise<TResult>): Promise<TResult[]> {
    items = is.promise(items) ? await items : items; // unwrap the promise if it is one

    if (items) {
        const result = [] as Promise<TResult>[];
        if (is.asyncIterable(items)) {
            for await (const item of items) {
                result.push(predicate(item)); // run the predicate on each item
            }
        } else {
            for (const item of items) {
                result.push(predicate(item)); // run the predicate on each item
            }
        }
        return Promise.all(result);
    }
    return []; // return an empty array if there is nothing to iterate over
}

interface Cursor<T> {
    identity: number;