How to fix property missing from an existing type?-CodePudding

I am converting an existing Node.js express application written in plain JS to TS. I understand why I get this error, but I do not know the correct way to fix it. The type "Request" comes from @types/express Do I have to extend this type to expect a property inside of body named product? I would to reuse the built-in types from @types/express as much as possible.

app.post('/something', function(req: Request) {
    if (req.body) product = req.body.product
                                     ^^^^^^^^
})

Error from Typescript server: Property 'product' does not exist on type 'ReadableStream'. (tsserver 2339)

CodePudding user response：

You can use 'as' keyboard like this:

import { Request, Response } from 'express';
interface IProduct{
   name: string;
   .
   .
}
app.post('/something', (req: Request) => {
    if (req.body) product = (req.body as { product: IProduct }).product
});

If you want to use @types/express you can use generic types:

import { Request, Response } from 'express';
interface IProduct{
   name: string;
   .
   .
}
app.post('/something', (req: Request<{}, {}, IProduct>) => {
    if (req.body) { product } = req.body;
});

CodePudding user response：

Wherever you're passing the body object from, make sure the object contains a product property. If you have a typed body, make sure to include the product as a parameter. For example,

type ReadableStream = { product: string }

Or before you pass body to app.post,

body: { product: "product" }

CodePudding user response：

You do not need to type the request.

but if you can type the request, follow this order:

interface P {}; /* params */
interface ResBody {}
interface ReqBody {}
interface ReqQuery {}

app.post('/something', function(req: Request<P, ResBody, ReqBody, ReqQuery>) {
    if (req.body) product = req.body.product
                                     
})

https://github.com/DefinitelyTyped/DefinitelyTyped/blob/master/types/express/index.d.ts#L112

and the error:

Property 'product' does not exist on type 'ReadableStream'.ts(2339)

that's because you need to import the request:

import { Request } = from 'express';

app.post('/something', function(req: Request) {
    if (req.body) product = req.body.product
})

the global Request interface is from the fetch API.