Typecript recursive types

Question

I would like to know if it is possible to type the following function without using any.

type MyType = {
  name: string,
  age: number,
  score: {
    prime: number,
  },
  prize: {
    first: {
      discount: number
    }
  }
}

export const trim = (
    myObj: MyType
): MyType => {
    const trimRecursive = (obj: any) => {
        for (let key in obj) {
            if (obj[key] && typeof obj[key] === 'object' && !Array.isArray(obj[key])) {
                trimRecursive(obj[key]);
            } else {
                if (typeof obj[key] === 'string') {
                    obj[key] = obj[key].trim();
                }
            }
        }
        return obj;
    };

    return trimRecursive(myObj);
};

Where are you using `any`? – Tony Troeff Feb 03 '22 at 14:36 — Tony Troeff, Feb 03 '22 at 14:36
sorry, I made an edit to my question, (obj :any) – Radex Feb 03 '22 at 16:39 — Radex, Feb 03 '22 at 16:39

Emanuel Lindström · Answer 1 · 2022-02-03T17:58:31.370

It might be a footgun, as this comment points out, but here's how I did it. I used forEach to be able to assign a type.


export const trim = <T>(myObj: T):T => {
  const trimRecursive = <T>(obj: T): T => {
    (Object.keys(obj) as Array<keyof T>).forEach((key) => {
      if (
        obj && typeof obj[key] === "object" && !Array.isArray(obj[key])
      ) {
        trimRecursive(obj[key])
      } else {
        if (typeof obj[key] === 'string') {
          obj[key] = (obj[key] as unknown as string).trim() as unknown as T[keyof T]
        }
    }
  })
    return obj
  }
  return trimRecursive(myObj)
}

Typecript recursive types

1 Answers1