reactjs - 连接 API 时出现 REACT、NODE、EXPRESS 错误
问题描述
我收到错误:
localhost/:1 Failed to load http://localhost:5000/api/hello: Response to preflight request doesn't pass access control check: No 'Access-Control-Allow-Origin' header is present on the requested resource. Origin 'http://localhost:3000' is therefore not allowed access. If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled.
这是我的异步 POST:
async function submitToServer(data){
try{
let response = await fetch('http://localhost:5000/api/hello', {
method: 'POST',
headers: {
'Content-type' : 'application/json',
},
body: JSON.stringify(data),
});
let responseJson = await response.json();
return responseJson;
} catch (error) {
console.error(error);
}
}
这是我的服务器:
const express = require('express');
const app = express();
const port = process.env.PORT || 5000;
app.get('/api/hello', (req, res) => {
res.send({ express: 'Hello From Express' });
});
app.listen(port, () => console.log(`Listening on port ${port}`));
我应该怎么做才能将此信息发送到 API?
我需要创建一个端点还是什么?
所以我安装了cors npm
.
现在我有这些错误:
POST localhost:5000/api/hello 404(未找到)
和
SyntaxError: 位置 0 处的 JSON 中的意外标记 <
我现在能做什么?
解决方案
您没有从快递服务器返回 JSON。
res.send({ express: 'Hello From Express' });
应该
res.json({ express: 'Hello From Express' });
此外,您定义了 的路线GET
,但您发送了一个POST
请求。所以你的处理程序应该是:
app.post('/api/hello', (req, res) => {
res.json({ express: 'Hello From Express' });
});