angular/packages/core/src/util/iterable.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
 */

import {getSymbolIterator} from './symbol';


export function isListLikeIterable(obj: any): boolean {
  if (!isJsObject(obj)) return false;
  return Array.isArray(obj) ||
      (!(obj instanceof Map) &&      // JS Map are iterables but return entries as [k, v]
       getSymbolIterator() in obj);  // JS Iterable have a Symbol.iterator prop
}

export function areIterablesEqual(
    a: any, b: any, comparator: (a: any, b: any) => boolean): boolean {
  const iterator1 = a[getSymbolIterator()]();
  const iterator2 = b[getSymbolIterator()]();

  while (true) {
    const item1 = iterator1.next();
    const item2 = iterator2.next();
    if (item1.done && item2.done) return true;
    if (item1.done || item2.done) return false;
    if (!comparator(item1.value, item2.value)) return false;
  }
}

export function iterateListLike(obj: any, fn: (p: any) => any) {
  if (Array.isArray(obj)) {
    for (let i = 0; i < obj.length; i++) {
      fn(obj[i]);
    }
  } else {
    const iterator = obj[getSymbolIterator()]();
    let item: any;
    while (!((item = iterator.next()).done)) {
      fn(item.value);
    }
  }
}

export function isJsObject(o: any): boolean {
  return o !== null && (typeof o === 'function' || typeof o === 'object');
}