Source: lib/util/functional.js

  1. /*! @license
  2.  * Shaka Player
  3.  * Copyright 2016 Google LLC
  4.  * SPDX-License-Identifier: Apache-2.0
  5.  */
  7. goog.provide('shaka.util.Functional');
  9. /**
  10.  * @summary A set of functional utility functions.
  11.  */
  12. shaka.util.Functional = class {
  13.   /**
  14.    * Creates a promise chain that calls the given callback for each element in
  15.    * the array in a catch of a promise.
  16.    *
  17.    * e.g.:
  18.    * Promise.reject().catch(callback(array[0])).catch(callback(array[1]));
  19.    *
  20.    * @param {!Array.<ELEM>} array
  21.    * @param {function(ELEM):!Promise.<RESULT>} callback
  22.    * @return {!Promise.<RESULT>}
  23.    * @template ELEM,RESULT
  24.    */
  25.   static createFallbackPromiseChain(array, callback) {
  26.     return array.reduce((promise, elem) => {
  27.       return promise.catch(() => callback(elem));
  28.     }, Promise.reject());
  29.   }
  32.   /**
  33.    * Returns the first array concatenated to the second; used to collapse an
  34.    * array of arrays into a single array.
  35.    *
  36.    * @param {!Array.<T>} all
  37.    * @param {!Array.<T>} part
  38.    * @return {!Array.<T>}
  39.    * @template T
  40.    */
  41.   static collapseArrays(all, part) {
  42.     return all.concat(part);
  43.   }
  45.   /**
  46.    * A no-op function that ignores its arguments.  This is used to suppress
  47.    * unused variable errors.
  48.    * @param {...*} args
  49.    */
  50.   static ignored(...args) {}
  53.   /**
  54.    * A no-op function.  Useful in promise chains.
  55.    */
  56.   static noop() {}
  59.   /**
  60.    * Returns if the given value is not null; useful for filtering out null
  61.    * values.
  62.    *
  63.    * @param {T} value
  64.    * @return {boolean}
  65.    * @template T
  66.    */
  67.   static isNotNull(value) {
  68.     return value != null;
  69.   }
  70. };