express typescript err抛出“any”警告

Question

我有一小段代码

import express from 'express';

const app = express();
const port = 3000;

app.get('/', (req, res) => {
  res.send('The sedulous hyena ate the antelope!');
});

app.listen(port, err => { //show error here
  if (err) {
    return console.error(err);
  }
  return console.log(`server is listening on ${port}`);
});

我想知道为什么会弹出这条信息

No overload matches this call.
  The last overload gave the following error.
    Argument of type '(err: any) => void' is not assignable to parameter of type '() => void'.ts(2769)

我没有为req和res声明类型，但是为什么typescript只为err显示error？

Answer 1

没有错误参数。

按住CTRL，然后点击听

它会打开index.d.ts，你会看到定义

  listen(port: number, hostname: string, backlog: number, callback?: () => void): http.Server;
  listen(port: number, hostname: string, callback?: () => void): http.Server;
  listen(port: number, callback?: () => void): http.Server;
  listen(callback?: () => void): http.Server;
  listen(path: string, callback?: () => void): http.Server;
  listen(handle: any, listeningListener?: () => void): http.Server;

正如您所看到的，回调不带参数