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javascripttypescriptexpresstypeorm

How to correctly type an 'omit' function in TypeScript to avoid error messages?

export const omit = <T, U extends keyof T>(obj: T, keys: U[]): Exclude<T, U> =>
  Object.keys(obj).reduce(  
    (acc: any, curr: any) => (keys.includes(curr) ? acc : { ...acc, [curr]: obj[curr] }),
    {}
  );

Getting an error message stating TS7053: Element implicitly has an 'any' type because expression of type 'any' can't be used to index type 'unknown'.

And would like to have no error messages and a correctly typed function.

Solution

  • It seems to me that you are trying to return an object so I believe you want to return Omit<T, U> and not Exclude<T, U> :

    You can see the difference here

    Here is how you can avoid your errors :

    export const omit = <T, U extends keyof T>(obj: T, keys: U[]): Omit<T, U> =>
  (Object.keys(obj) as U[]).reduce(
    (acc, curr) => (keys.includes(curr) ? acc : { ...acc, [curr]: obj[curr] }),
    {} as Omit<T, U>
  );