Question

我想使用Express获取数据。这是代码：

const express = require('express');
const app = express();
const cors = require('cors');
require('dotenv/config');

// Middlewares
app.use(cors());
app.use(express.json());

// Routes
const postRouter = require('./routes/posts');
app.use('/posts', postRouter);

// Mongoose connect
const mongoose = require('mongoose');
mongoose.connect(
    process.env.DB_CONNECTION,
    { useNewUrlParser: true },
    () => console.log("You are connected to MongoDB")
);

// Port listen
app.listen(2998);

这些node + express代码可以在Postman中完美运行。

但是在使用JavaScript即时获取时，它始终显示CORS错误。这是JS代码：

let url = "https://localhost:2998/posts/"
    fetch(url)
    .then(result => {
        console.log(result);    
    })
    .then(data => {
        console.log("data: " + data)
    });

控制台显示：

跨域请求被阻止：“同源起源”策略禁止读取https://localhost:2998/posts/处的远程资源。（原因：CORS请求未成功。）

。。。。

已解决！它只是无法运行https协议，因此我需要将其更改为http://localhost/2998。不过，我不知道为什么会发生这种情况

Answer 1

我相信您没有设置CORS选项。请尝试以下操作：

const express = require('express');
const app = express();
const cors = require('cors');
require('dotenv/config');

// CORS Options: But customise according to your needs
const options = {
    allowedHeaders: ["Origin", "Content-Type", "Accept", "Authorization"],
    methods: "GET,HEAD,OPTIONS,PUT,PATCH,POST,DELETE",
    origin: "*",
    preflightContinue: false
};

// Middlewares
app.use(cors(options));
app.use(express.json());

// Routes
const postRouter = require('./routes/posts');
app.use('/posts', postRouter);

// Mongoose connect
const mongoose = require('mongoose');
mongoose.connect(
    process.env.DB_CONNECTION,
    { useNewUrlParser: true },
    () => console.log("You are connected to MongoDB")
);

// Port listen
app.listen(2998);

为什么我的Express中的cors处理不起作用？

1 个答案: