如何使用express在回调函数之间传递值？ [复制]答案

【问题标题】：How to pass a value between callback functions using express? [duplicate]如何使用express在回调函数之间传递值？ [复制]
【发布时间】：2021-02-15 11:49:41
【问题描述】：

我正在尝试文档附带的express route handlers 以特定顺序进行一系列函数调用，所以我想将一个值从cb0 传递给cb1（或cb2），目前我在 req 对象中设置一个属性并从另一个处理程序访问它，这工作正常。

const express = require('express');
const app = express();
const PORT = 8000;

const cb0 = function (req, res, next) {
  console.log('CB0');
  req.cb0val = 'Hello';
  next();
}

const cb1 = function (req, res, next) {
  console.log('CB1');
  req.cb1val = 'World';
  next();
}

const cb2 = function (req, res) {
  res.send(`Hey, ${req.cb0val} ${req.cb1val}`);
}

app.get('/', [cb0, cb1, cb2])

app.listen(PORT, () => {
  console.log(`⚡️[server]: Server is running at https://localhost:${PORT}`);
});

使用typescript时出现问题

import express from 'express';
const app = express();
const PORT = 8000;

const cb0: express.RequestHandler = function (req: express.Request, res: express.Response, next: Function) {
  console.log('CB0');
  req.cb0val = 'Hello';
  next();
}

const cb1: express.RequestHandler = function (req: express.Request, res: express.Response, next: Function) {
  console.log('CB1');
  req.cb1val = 'World';
  next();
}

const cb2: express.RequestHandler = function (req: express.Request, res: express.Response) {
  res.send(`Hey, ${req.cb0val} ${req.cb1val}`);
}

app.get('/example/c', [cb0, cb1, cb2])

app.listen(PORT, () => {
  console.log(`⚡️[server]: Server is running at https://localhost:${PORT}`);
});

因为我将req 的类型设置为express.Request，所以我无法设置该类型的新属性，出现以下错误：

index.ts:7:7 - error TS2339: Property 'cb0val' does not exist on type 'Request<ParamsDictionary, any, any, ParsedQs>'.

7   req.cb0val = 'Hello';
        ~~~~~~
index.ts:13:7 - error TS2339: Property 'cb1val' does not exist on type 'Request<ParamsDictionary, any, any, ParsedQs>'.

13   req.cb1val = 'World';
         ~~~~~~
index.ts:18:24 - error TS2339: Property 'cb0val' does not exist on type 'Request<ParamsDictionary, any, any, ParsedQs>'.

18   res.send(`Hey, ${req.cb0val} ${req.cb1val}`);
                          ~~~~~~
index.ts:18:38 - error TS2339: Property 'cb1val' does not exist on type 'Request<ParamsDictionary, any, any, ParsedQs>'.

18   res.send(`Hey, ${req.cb0val} ${req.cb1val}`);
                                        ~~~~~~

在不将express.Request 的类型更改为any 的情况下，处理这种情况的正确方法是什么？

【问题讨论】：

标签： typescript express

【解决方案1】：

你可以使用一种叫做声明合并的东西。

在项目的某处创建一个名为express.d.ts 的文件。这通常在项目根目录 (@types/express.d.ts) 的 @types 文件夹中创建。

这个文件的内容应该是

declare namespace Express {
    interface Request {
        cb0val: string
        // other custom properties ...
    }
}

在您的 tsconfig 中，设置 typeRoot 或将新文件添加到 types 字段。

"typeRoots": [
  "@types/",
  "node_modules/@types/"
]

【讨论】：