在 node.js 中不存在相关性 ID

Question

I am trying to add correlationId using express-correlation-id. I am exactly following the page: https://www.npmjs.com/package/express-correlation-id . I've imported the express-correlation-id pkg and have found it in the package.json and node modules.

But when i tried to get req.correlationId(), it always said:

Property 'correlationId' dosn't exist on type 'Request<ParamsDictionary, any, any, ParsedQs>'.

I'm using TypeScript and Express, this is what the code looks like:

import correlator = require("express-correlation-id");
app.use(correlator());
app.get('/', (req, res) => {
    req.correlationId();    // where the error occurs
});

Answer 1

Since this package is written in js language, there are no type definition files for typescript, so you need to extend the Express.Request interface by yourself, add the correlationId method to the interface.

Package versions:

• "typescript": "^3.9.7"
• "express-correlation-id": "^1.3.1",
• "express": "^4.17.1",

Eg

server.ts :

import express from 'express';
import correlator = require('express-correlation-id');

declare global {
  namespace Express {
    export interface Request {
      correlationId(): string;
    }
  }
}

const app = express();

app.use(correlator());
app.get('/', (req, res) => {
  req.correlationId();
});

Answer 2

This is because the property correlationId doesn't exist in the typing of req .

So, if you see the typing of req is:

export interface Request<P = ParamsDictionary, ResBody = any, ReqBody = any, ReqQuery = ParsedQs> extends http.IncomingMessage, Express.Request {

So, you must create a new Request type with the new functions that you're going to use. For your case:

import express from "express";
import correlator = require("express-correlation-id");
import { ParamsDictionary, Request } from "express-serve-static-core";
import { ParsedQs } from "qs";

const app = express();

interface CustomReq<P = ParamsDictionary, ResBody = any, ReqBody = any, ReqQuery = ParsedQs> extends Request<P, ResBody, ReqBody, ReqQuery> {
    // extended options
    correlationId: () => any;
}

app.use(correlator());
app.get('/', (req: CustomReq, res) => {
    req.correlationId(); // OK
});

As you see in the code above, my new Request is CustomReq and I use the new type for the req .