angular-docs-cn/packages/core/src/util/array_utils.ts

/**
 * @license
 * Copyright Google Inc. All Rights Reserved.
 *
 * Use of this source code is governed by an MIT-style license that can be
 * found in the LICENSE file at https://angular.io/license
 */

/**
* Equivalent to ES6 spread, add each item to an array.
*
* @param items The items to add
* @param arr The array to which you want to add the items
*/
export function addAllToArray(items: any[], arr: any[]) {
  for (let i = 0; i < items.length; i++) {
    arr.push(items[i]);
  }
}

/**
 * Flattens an array.
 */
export function flatten(list: any[], dst?: any[]): any[] {
  if (dst === undefined) dst = list;
  for (let i = 0; i < list.length; i++) {
    let item = list[i];
    if (Array.isArray(item)) {
      // we need to inline it.
      if (dst === list) {
        // Our assumption that the list was already flat was wrong and
        // we need to clone flat since we need to write to it.
        dst = list.slice(0, i);
      }
      flatten(item, dst);
    } else if (dst !== list) {
      dst.push(item);
    }
  }
  return dst;
}

export function deepForEach<T>(input: (T | any[])[], fn: (value: T) => void): void {
  input.forEach(value => Array.isArray(value) ? deepForEach(value, fn) : fn(value));
}

export function addToArray(arr: any[], index: number, value: any): void {
  // perf: array.push is faster than array.splice!
  if (index >= arr.length) {
    arr.push(value);
  } else {
    arr.splice(index, 0, value);
  }
}

export function removeFromArray(arr: any[], index: number): any {
  // perf: array.pop is faster than array.splice!
  if (index >= arr.length - 1) {
    return arr.pop();
  } else {
    return arr.splice(index, 1)[0];
  }
}

export function newArray<T = any>(size: number): T[];
export function newArray<T>(size: number, value: T): T[];
export function newArray<T>(size: number, value?: T): T[] {
  const list: T[] = [];
  for (let i = 0; i < size; i++) {
    list.push(value !);
  }
  return list;
}