[Typescript] Iterating Over Object Keys in Typescript

import { expect, it, vitest } from 'vitest';

interface User {
  id: number;
  name: string;
}

function printUser(user: User) {
  Object.keys(user).forEach((key) => {
    // @ts-expect-error
    console.log(user[key]);
  });
}

it('Should log all the keys of the user', () => {
  const consoleSpy = vitest.spyOn(console, 'log');

  printUser({
    id: 1,
    name: 'Waqas',
  });

  expect(consoleSpy).toHaveBeenCalledWith(1);
  expect(consoleSpy).toHaveBeenCalledWith('Waqas');
});

After Object.keys, the keyis stringtype, therefore when we do user[key], Typescript complians.

 

Two way to resolve the issues

 

1. Widen the restriction

function printObjectValue(obj: Record<string, any>) {
  Object.keys(obj).forEach((key) => {
    console.log(obj[key]);
  });
}

Using a generic function to print object value.

 

2. Using as

function printUser(user: User) {
  Object.keys(user).forEach((key) => {
    console.log(user[key as keyof User]);
  });
}