shaka-player/lib/util/array_utils.js

/**
 * @license
 * Copyright 2016 Google Inc.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *     http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

goog.provide('shaka.util.ArrayUtils');


/**
 * @namespace shaka.util.ArrayUtils
 * @summary Array utility functions.
 */


shaka.util.ArrayUtils = class {
  /**
   * Returns whether the two values contain the same value.  This correctly
   * handles comparisons involving NaN.
   * @param {T} a
   * @param {T} b
   * @return {boolean}
   * @template T
   */
  static defaultEquals(a, b) {
    // NaN !== NaN, so we need to special case it.
    if (typeof a === 'number' &&
        typeof b === 'number' && isNaN(a) && isNaN(b)) {
      return true;
    }
    return a === b;
  }


  /**
   * Remove given element from array (assumes no duplicates).
   * @param {!Array.<T>} array
   * @param {T} element
   * @template T
   */
  static remove(array, element) {
    const index = array.indexOf(element);
    if (index > -1) {
      array.splice(index, 1);
    }
  }


  /**
   * Count the number of items in the list that pass the check function.
   * @param {!Array.<T>} array
   * @param {function(T):boolean} check
   * @return {number}
   * @template T
   */
  static count(array, check) {
    let count = 0;

    for (const element of array) {
      count += check(element) ? 1 : 0;
    }

    return count;
  }


  /**
   * Determines if the given arrays contain the same elements.
   *
   * @param {!Array.<T>} a
   * @param {!Array.<T>} b
   * @param {function(T, T):boolean=} compareFn
   * @return {boolean}
   * @template T
   */
  static hasSameElements(a, b, compareFn) {
    if (!compareFn) {
      compareFn = shaka.util.ArrayUtils.defaultEquals;
    }
    if (a.length != b.length) {
      return false;
    }

    const copy = b.slice();
    for (const item of a) {
      const idx = copy.findIndex((other) => compareFn(item, other));
      if (idx == -1) {
        return false;
      }
      // Since order doesn't matter, just swap the last element with
      // this one and then drop the last element.
      copy[idx] = copy[copy.length - 1];
      copy.pop();
    }

    return copy.length == 0;
  }
};