What are the steps to correct a missing property in an established type?

Question

What are the steps to correct a missing property in an established type?

Currently, I am in the process of converting an existing Node.js + express application from plain JS to TypeScript. Although I understand why I am encountering this error, I am unsure about the correct approach to resolve it. The type "Request" is coming from @types/express. Should I extend this type to include a property named product inside the body? My goal is to utilize the predefined types provided by @types/express wherever 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)

typescript

Answer 1

Answer №1

If you ever need to access 'as' keyboard, here is how you can do it:

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

In case you prefer using @types/express with generic types:

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

Answer 2

If you ever need to access 'as' keyboard, here is how you can do it:

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

In case you prefer using @types/express with generic types:

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

Answer 3

Answer №2

Ensure that the body object being passed contains a product property from wherever it originated. If you are working with a typed body, remember to include the product as a parameter. In other words,

type ReadableStream = { product: string }

Alternatively, before passing body to app.post,

body: { product: "product" }

Answer 4

Ensure that the body object being passed contains a product property from wherever it originated. If you are working with a typed body, remember to include the product as a parameter. In other words,

type ReadableStream = { product: string }

Alternatively, before passing body to app.post,

body: { product: "product" }

Answer 5

Answer №3

You are not required to manually input the request.

However, if you choose to enter the request, please adhere to this sequence:

interface P {}; /* parameters */
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

Furthermore, an error is noted:

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

This issue arises due to the requirement 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 can be found within the fetch API.

Answer 6

You are not required to manually input the request.

However, if you choose to enter the request, please adhere to this sequence:

interface P {}; /* parameters */
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

Furthermore, an error is noted:

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

This issue arises due to the requirement 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 can be found within the fetch API.

What are the steps to correct a missing property in an established type?

Answer №1

Answer №2

Answer №3

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