Angular 6 - 请求的资源上不存在'Access-Control-Allow-Origin'标头

Question

我有一个 Angular 6 项目，它有一个指向服务器的服务.js

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

当我将服务指向http://localhost:3000/api/posts(服务器.js位置时，出现此错误：

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.

这是服务器.js代码：

// 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}`));

我的问题是：

如何获得服务器.js以允许此调用？

Answer 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')
})

Answer 2

太好了！ 您需要启用可以发出请求的域 CORS！ 你可以试试

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

或者你可以设置localhost:4200或类似的东西

试试看，告诉我是否有效！谢谢！希望这有帮助！

Answer 3

由于您使用的是 express，因此您可以创建一个中间件并使用它来重定向所有端点。这是相同的工作片段：

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();

})

在你设定路线之前把它放在你身上，你应该很好。

查看：了解使用 express.js 在路由端点中使用中间件的 https://github.com/pyronlaboratory/phoenix/blob/master/messageboard/backend/server.js。