jupyterlab/packages/coreutils/src/debounce.ts

import { PromiseDelegate } from '@phosphor/coreutils';

// Copyright (c) Jupyter Development Team.
// Distributed under the terms of the Modified BSD License.

/**
 * Returns a debounced function that can be called multiple times safely and
 * only executes the underlying function once per `interval`.
 *
 * @param fn - The function to debounce.
 *
 * @param interval - The debounce interval; defaults to 500ms.
 */
export function debounce(fn: () => any, interval = 500): () => Promise<void> {
  let debouncer = 0;
  return () => {
    const delegate = new PromiseDelegate<void>();
    clearTimeout(debouncer);
    debouncer = setTimeout(async () => {
      delegate.resolve(void (await fn()));
    }, interval);
    return delegate.promise;
  };
}