don't use object as a type

Question

I am getting the lint error:

don't use object as a type

When I use object as a type, example follows:

export const myFunc = (obj: object): string => {
  return obj.toString()
}

Any idea what type I should give to an object with unknown properties?

If it helps the object in question is NOT an array (which I know is strictly an object in JS)

Thanks in advance

obviously, the whole function is useless - its just an example - thx — danday74, Nov 16 '20 at 10:09
Does this answer your question? [How can I solve this error 'don't use object as a type'?](https://stackoverflow.com/questions/64962822/how-can-i-solve-this-error-dont-use-object-as-a-type) — Aleksi, Mar 11 '21 at 03:03

score 8 · Accepted Answer · answered Nov 16 '20 at 04:51

8

There's a few different ways to do this. Generally I feel the need for this is a bit of an anti-pattern.

But I would probably go for Record<string, any>, if that covers it for you.

answered Nov 16 '20 at 04:51

Evert

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score 7 · Answer 2 · answered Nov 16 '20 at 07:36

I think that the best approach here is to use generic:

export const myFunc = <T extends { toString: () => string }>(obj: T): string => {
    return obj.toString()
}

myFunc(2) // no error
myFunc({}) // no error

If you want restrict your arguments to only object, then yes, @Evert's solution is Ok. But for the sake of type safety it is better to use unknown instead of any:

Record<string, unknown>

score 3 · Answer 3 · answered Mar 11 '21 at 03:05

Here's a concrete example of why the linter rule advices against using the object type:

function foo(obj: object) {
    for (const key in obj) {
        const val = obj[key]; // Compilation error: type 'string' can't be used to index type '{}'
    }
}

function bar(obj: { [key: string]: unknown }) {
    for (const key in obj) {
        const val = obj[key]; // works :)
    }
}

don't use object as a type

3 Answers3

Linked