面临Mongoose的问题。
import express from 'express';
import Countries from '../models/countries.mjs';
const router = new express.Router();
router.get('/countries-data', async (req, res) => {
try {
let countries =
await Countries.find({})
.select(
'-_id specimenDate dailyLabConfirmedCases changeInDailyCases')
.sort('specimenDate');
if (!countries) return res.status(500).send();
res.json(countries);
} catch (err) {
res.status(500).send();
}
});
这段代码按预期工作,但我决定删除async/await并使用find((.then((:
import express from 'express';
import Countries from '../models/countries.mjs';
const router = new express.Router();
router.get('/countries-data', (_, res) => {
Countries.find({})
.select('-_id specimenDate dailyLabConfirmedCases changeInDailyCases')
.sort('specimenDate')
.then((countries) => {
if (!countries) throw Error('no data');
res.json(countries);
})
.catch(res.status(500).send());
});
这一个在尝试发送json数据时出现异常:
未处理的PromiseRetentionWarning:Error[ERR_HTTP_HEADERS_SENT]:在将标头发送到客户端后无法设置标头
我真的不知道我做错了什么。为什么捕获没有得到承诺例外?有什么建议吗?
我认为问题源于您在catch
块中发送的响应,因为catch
接受了一个回调函数,如果有错误,该函数会返回一个错误。
试试这个:
import express from 'express';
import Countries from '../models/countries.mjs';
const router = new express.Router();
router.get('/countries-data', (_, res) => {
Countries.find({})
.select('-_id specimenDate dailyLabConfirmedCases changeInDailyCases')
.sort('specimenDate')
.then((countries) => {
if (!countries) throw Error('no data');
res.json(countries);
})
// refactor your code like this
.catch((err)=>{
res.status(500).send(err)
});
});