1/*
2 * Copyright (c) 2020 Huawei Device Co., Ltd.
3 * Licensed under the Apache License, Version 2.0 (the "License");
4 * you may not use this file except in compliance with the License.
5 * You may obtain a copy of the License at
6 *
7 *     http://www.apache.org/licenses/LICENSE-2.0
8 *
9 * Unless required by applicable law or agreed to in writing, software
10 * distributed under the License is distributed on an "AS IS" BASIS,
11 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
12 * See the License for the specific language governing permissions and
13 * limitations under the License.
14 */
15export const ObserverStack = {
16  stack: [],
17  push(observer) {
18    this.stack.push(observer);
19  },
20  pop() {
21    return this.stack.pop();
22  },
23  top() {
24    return this.stack[this.stack.length - 1];
25  }
26};
27
28export const SYMBOL_OBSERVABLE = '__ob__';
29
30export const canObserve = target => typeof target === 'object' && target !== null;
31
32export const defineProp = (target, key, value) => {
33  Object.defineProperty(target, key, { enumerable: false, value });
34};
35