CODEWITHSUNDEEP
typescriptjestjs
Tomer Amir
Tomer Amir

Reputation: 1585

Property 'prototype' does not exist

I am trying to use jest and mock ioredis in typescript.

The issue is that I am getting an error from typescript that:

tests/__mocks__/ioredis.ts(5,9): error TS2339: Property 'prototype' does not exist on type 'Redis''

The code does work, but I would like to solve this error. Here is my mock:

// tests/__mocks__/ioredis.ts
import { Redis } from 'ioredis';

const IORedis: Redis = jest.genMockFromModule<Redis>('ioredis');

IORedis.prototype.hgetall = jest.fn().mockImplementation(async (key: string) => {
    // Some mock implementation
});

module.exports = IORedis;

What am I doing wrong?

Upvotes: 6

Views: 12776

Answers (2)

Adverbly
Adverbly

Reputation: 2139

If the type you need to extend is generic, you can use type variables when creating the union type.

interface IPrototype { prototype: any; }
type ExtendedType<A, B> = IPrototype & BasicType<A, B>;

Then you can cast using

(myvar as ExtendedType<any, any>).prototype

Upvotes: 1

kimy82
kimy82

Reputation: 4475

There is a no perfect solution.

First define a intereface with prototype property:

interface IPrototype { prototype: any; }

The use IORedis like this to have access to prototype and ohter Redis methods.

(IORedis as IPrototype & Redis).prototype ...

Another option might be to declare your const like this:

interface IPrototype { prototype: any; }
type MyRedis = Redis & IPrototype;
const IORedis: MyRedis = jest.genMockFromModule<MyRedis>('ioredis');

Hope that helps!

Upvotes: 6

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