/** @license
* Copyright 2016 Google LLC
* SPDX-License-Identifier: Apache-2.0
*/
goog.provide('shaka.util.Functional');
goog.require('shaka.Deprecate');
/**
* @summary A set of functional utility functions.
*/
shaka.util.Functional = class {
/**
* Creates a promise chain that calls the given callback for each element in
* the array in a catch of a promise.
*
* e.g.:
* Promise.reject().catch(callback(array[0])).catch(callback(array[1]));
*
* @param {!Array.<ELEM>} array
* @param {function(ELEM):!Promise.<RESULT>} callback
* @return {!Promise.<RESULT>}
* @template ELEM,RESULT
*/
static createFallbackPromiseChain(array, callback) {
return array.reduce((promise, elem) => {
return promise.catch(() => callback(elem));
}, Promise.reject());
}
/**
* Returns the first array concatenated to the second; used to collapse an
* array of arrays into a single array.
*
* @param {!Array.<T>} all
* @param {!Array.<T>} part
* @return {!Array.<T>}
* @template T
*/
static collapseArrays(all, part) {
return all.concat(part);
}
/**
* A no-op function that ignores its arguments. This is used to suppress
* unused variable errors.
* @param {...*} args
*/
static ignored(...args) {}
/**
* A no-op function. Useful in promise chains.
*/
static noop() {}
/**
* Returns if the given value is not null; useful for filtering out null
* values.
*
* @param {T} value
* @return {boolean}
* @template T
*/
static isNotNull(value) {
return value != null;
}
/**
* Calls a factory function while allowing it to be a constructor for
* reverse-compatibility.
*
* @param {function():!T} factory
* @return {!T}
* @template T
*/
static callFactory(factory) {
// See https://stackoverflow.com/q/10428603/1208502
// eslint-disable-next-line no-restricted-syntax
const obj = Object.create(factory.prototype || Object.prototype);
// If this is a constructor, call it with our newly created object to
// initialize it; if this isn't a constructor, the "this" shouldn't be used
// since it should be "undefined".
let ret = factory.call(obj); // eslint-disable-line no-restricted-syntax
// If it didn't return anything, assume it is a constructor and return our
// "this" value instead.
if (!ret) {
shaka.Deprecate.deprecateFeature(4,
'Factories requiring new',
'Factories should be plain functions');
ret = obj;
}
return ret;
}
};