Question

我无法连接我连接的node.js后端代码，当它们在后端运行时工作正常，但是当我尝试在前端使用这些函数时react.js它没有工作。我收到意外令牌的错误，我认为是因为它取错了数据。

这是我的后端桌面\ test \ src \ users.js：

var express  = require('express');

var app   = express();                             

var Firebase = require('firebase');

var morgan = require('morgan');      

var bodyParser = require('body-parser');    

var Rebase = require('re-base');

app.use(function(req, res, next) { 

res.setHeader("Access-Control-Allow-Origin", "*");

res.header("Access-Control-Allow-Methods", "POST, PUT, OPTIONS, DELETE, GET");

res.header("Access-Control-Max-Age", "3600");

res.header("Access-Control-Allow-Headers", "Content-Type, Access-Control-Allow-Headers, Authorization, X-Requested-With");

next();

});


Firebase.initializeApp({

apiKey: test.apiKey,

authDomain: test.authDomain,

databaseURL: test.databaseURL,

projectId: test.projectId,

storageBucket: test.storageBucket,

messagingSenderId: test.messagingSenderId,

serviceAccount: './testapp.json', 

});


var db = Firebase.database();

var usersRef = db.ref("Users/");
console.log("reached here.");
 app.get('/api/users', function(req, res) 
 {
     var array = [];
     usersRef.on("value", function(snapshot)
     {
         snapshot.forEach(function(data) 
         {
             var usernames =data.child("username").val();
             var user = { "username": usernames};
             array.push(user);
         });
          res.json(array);
      });
     });
     app.listen(8000);

 console.log("port is 8000");

desktop \ test \ src \ test.js包含我的firebase信息。我把X放在这里只是为了显示它。

module.exports = {     
apiKey: "XXXXXXXXXXXXXXXXXXXXXXUrQT8_WyGeZYSkNIA",
authDomain: "authentication-efba4.firebaseapp.com",
databaseURL: "https://authentication-efba4.firebaseio.com",
projectId: "authentication-efba4",
storageBucket: "authentication-efba4.appspot.com",
messagingSenderId: "XXXXX8179075"

 };

这是我的前端桌面\ test \ src \ App.js：

import React, { Component } from 'react';
import './App.css';

class App extends Component {
  state = {users: []}

  componentDidMount() {
    fetch('/users')
      .then(res => res.json())
      .then(users => this.setState({ users }));
  }

  render() {
    return (
      <div className="App">
        <h1>Users</h1>
        {this.state.users.map(user =>
          <div key={user.id}>{user.username}</div>
        )}
     </div>
    );
  }
}

export default App;

它不是从数据库中获取数据，我在运行纱线启动时甚至无法编译它。我收到这个错误：

Unhandled Rejection (SyntaxError): Unexpected token < in JSON at position 0
 6 | 
 7 | componentDidMount() {
 8 |   fetch('/users')
 9 |     .then(res => res.json()) <--
10 |     .then(users => this.setState({ users }));
11 | }
12 |

Answer 1

使用以下功能拍摄数据库快照

var ref = db.ref("server/saving-data/fireblog/posts");

// Attach an asynchronous callback to read the data at our posts reference
ref.on("value", function(snapshot) {
  console.log(snapshot.val());
}, function (errorObject) {
  console.log("The read failed: " + errorObject.code);
});

参考：https://firebase.google.com/docs/database/admin/retrieve-data

使用react.js连接API node.js后端（firebase）

1 个答案: