Angular 6 - No 'Access-Control-Allow-Origin

问题:

I have an Angular 6 project, which has a service with is pointing to a server.js

Angular is on port: 4200 and Server.js is on port: 3000.

When I point the service to http://localhost:3000/api/posts (Server.js location), I'm getting this error:

Failed to load http://localhost:3000/api/posts: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:4200' is therefore not allowed access.

Here is the server.js code:

// Get dependencies
const express = require('express');
const path = require('path');
const http = require('http');
const bodyParser = require('body-parser');

// Get our API routes
const api = require('./server/routes/api');

const app = express();

// Parsers for POST data
app.use(bodyParser.json());
app.use(bodyParser.urlencoded({ extended: false }));

// Point static path to dist
app.use(express.static(path.join(__dirname, 'dist')));

// Set our api routes
app.use('/api', api);

// Catch all other routes and return the index file
app.get('*', (req, res) => {
  res.sendFile(path.join(__dirname, 'dist/myproject/index.html'));
});

/**
 * Get port from environment and store in Express.
 */
const port = process.env.PORT || '3000';
app.set('port', port);

/**
 * Create HTTP server.
 */
const server = http.createServer(app);

/**
 * Listen on provided port, on all network interfaces.
 */
server.listen(port, () => console.log(`API running on localhost:${port}`));

My question is:

How to I get server.js to allow this call?

回答1:

If you are using Express, you can try this cors package.

EDIT:

var express = require('express')
var cors = require('cors')
var app = express()

app.use(cors())

app.get('/products/:id', function (req, res, next) {
  res.json({msg: 'This is CORS-enabled for all origins!'})
})
app.listen(80, function () {
  console.log('CORS-enabled web server listening on port 80')
})

回答2:

Great! you need to enable domain CORS that can make requests! You can try that

app.use(function(req, res, next) {
  res.header("Access-Control-Allow-Origin", "*");
  res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");
  next();
});
"Access-Control-Allow-Origin", "*" -> used to accept all domains

Or you can just set localhost:4200 or something like that

Try that and tell me if worked! Thanks! Hope this helps!

回答3:

Since you are using express, you could create a middleware and use it to redirect all your endpoints. Here is a working snippet of the same:

app.use((req,res,next) => {
            
     res.header("Access-Control-Allow-Origin","*");
     res.header("Access-Control-Allow-Methods", "POST, GET");
     res.header("Access-Control-Allow-Header","Origin, X-Requested-With, Content-Type, Accept");
     next();
            
})

Place it before you are setting your routes and you should be good.

Check out: https://github.com/pyronlaboratory/phoenix/blob/master/messageboard/backend/server.js for understanding usage of middlewares in routing endpoints using express.js.