Source: lib/util/array_utils.js

  1. /**
  2.  * @license
  3.  * Copyright 2016 Google Inc.
  4.  *
  5.  * Licensed under the Apache License, Version 2.0 (the "License");
  6.  * you may not use this file except in compliance with the License.
  7.  * You may obtain a copy of the License at
  8.  *
  9.  *     http://www.apache.org/licenses/LICENSE-2.0
  10.  *
  11.  * Unless required by applicable law or agreed to in writing, software
  12.  * distributed under the License is distributed on an "AS IS" BASIS,
  13.  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
  14.  * See the License for the specific language governing permissions and
  15.  * limitations under the License.
  16.  */
  18. goog.provide('shaka.util.ArrayUtils');
  21. /**
  22.  * @namespace shaka.util.ArrayUtils
  23.  * @summary Array utility functions.
  24.  */
  27. /**
  28.  * Returns whether the two values contain the same value.  This correctly
  29.  * handles comparisons involving NaN.
  30.  * @param {T} a
  31.  * @param {T} b
  32.  * @return {boolean}
  33.  * @template T
  34.  */
  35. shaka.util.ArrayUtils.defaultEquals = function(a, b) {
  36.   // NaN !== NaN, so we need to special case it.
  37.   if (typeof a === 'number' && typeof b === 'number' && isNaN(a) && isNaN(b)) {
  38.     return true;
  39.   }
  40.   return a === b;
  41. };
  44. /**
  45.  * Remove duplicate entries from an array.  Order N^2, so use with caution.
  46.  * @param {!Array.<T>} array
  47.  * @param {function(T, T): boolean=} compareFn An optional function which
  48.  *   will be used to compare items in the array.
  49.  * @return {!Array.<T>}
  50.  * @template T
  51.  */
  52. shaka.util.ArrayUtils.removeDuplicates = function(array, compareFn) {
  53.   if (!compareFn) {
  54.     compareFn = shaka.util.ArrayUtils.defaultEquals;
  55.   }
  57.   let result = [];
  58.   for (const item of array) {
  59.     const idx = shaka.util.ArrayUtils.indexOf(result, item, compareFn);
  60.     if (idx == -1) {
  61.       result.push(item);
  62.     }
  63.   }
  64.   return result;
  65. };
  68. /**
  69.  * Find an item in an array.  For use when comparison of entries via == will
  70.  * not suffice.
  71.  * @param {!Array.<T>} array
  72.  * @param {T} value
  73.  * @param {function(T, T): boolean} compareFn A function which will be used to
  74.  *   compare items in the array.
  75.  * @return {number} The index, or -1 if not found.
  76.  * @template T
  77.  */
  78. shaka.util.ArrayUtils.indexOf = function(array, value, compareFn) {
  79.   for (let i = 0; i < array.length; ++i) {
  80.     if (compareFn(array[i], value)) {
  81.       return i;
  82.     }
  83.   }
  84.   return -1;
  85. };
  88. /**
  89.  * Remove given element from array (assumes no duplicates).
  90.  * @param {!Array.<T>} array
  91.  * @param {T} element
  92.  * @template T
  93.  */
  94. shaka.util.ArrayUtils.remove = function(array, element) {
  95.   let index = array.indexOf(element);
  96.   if (index > -1) {
  97.     array.splice(index, 1);
  98.   }
  99. };
  102. /**
  103.  * Count the number of items in the list that pass the check function.
  104.  * @param {!Array.<T>} array
  105.  * @param {function(T):boolean} check
  106.  * @return {number}
  107.  * @template T
  108.  */
  109. shaka.util.ArrayUtils.count = function(array, check) {
  110.   let count = 0;
  112.   array.forEach(function(element) {
  113.     count += check(element) ? 1 : 0;
  114.   });
  116.   return count;
  117. };