使用firebase在ionic 2中实现like/like函数

npm install firebase --save

export const firebaseConfig = {
  apiKey: "YOUR_API_KEY",
  authDomain: "YOUR_AUTH_DOMAIN",
  databaseURL: "YOUR_DATABASE_URL",
  projectId: "YOUR_PROJECT_ID",
  storageBucket: "YOUR_STORAGE_BUCKET",
  messagingSenderId: "YOUR_MESSAGING_SENDER_ID"
};

import { Component } from '@angular/core';
import * as firebase from 'firebase';
import { firebaseConfig } from '../firebase.config';

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  constructor() {
    firebase.initializeApp(firebaseConfig);
  }
}

import { Component } from '@angular/core';
import * as firebase from 'firebase';
import { firebaseConfig } from '../firebase.config';

@Component({
  selector: 'page-home',
  templateUrl: 'home.html'
})
export class HomePage {
  likeCount: number = 0;
  isLiked: boolean = false;

  constructor() {
    firebase.initializeApp(firebaseConfig);
    this.getLikeCount();
    this.checkIfLiked();
  }

  getLikeCount() {
    firebase.database().ref('likes').on('value', (snapshot) => {
      this.likeCount = snapshot.val();
    });
  }

  checkIfLiked() {
    firebase.database().ref('users/user1').on('value', (snapshot) => {
      this.isLiked = snapshot.val().liked;
    });
  }

  like() {
    firebase.database().ref('likes').transaction((currentCount) => {
      return (currentCount || 0) + 1;
    });

    firebase.database().ref('users/user1').set({
      liked: true
    });
  }

  unlike() {
    firebase.database().ref('likes').transaction((currentCount) => {
      return (currentCount || 0) - 1;
    });

    firebase.database().ref('users/user1').set({
      liked: false
    });
  }
}