@webex/common/src/tap.js

Common utilities for Cisco Webex

/*!
 * Copyright (c) 2015-2020 Cisco Systems, Inc. See LICENSE file.
 */

/**
 * Injects code into a promise chain without modifying the promise chain's result
 * @param {Function} fn
 * @returns {Promise}
 * @example
 * function f() {
 *   return Promise.resolve(5);
 * }
 *
 * f()
 *   .then(tap(() => 12))
 *   // => 5
 */
export default function tap(fn) {
  return (r) =>
    new Promise((resolve) => {
      resolve(fn(r));
    })
      .then(() => r)
      .catch(() => r);
}