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The Strictest TypeScript Config

Vladyslav Zubko on December 13, 2023

Most people know that to make projects using TypeScript "strict" in terms of typing, you need to enable the "strict": true option in the tsconfig. ...

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Vladyslav Zubko • Dec 13 '23 • Edited

Hey @artxe2 !

I think the issue lies more in the for...of/for...in loop, as it returns a string for a key variable. If you typecast it, everything will be fine 🙂

for (let key of Object.keys(obj)) {
  const typeKey = key as keyof typeof obj;

  obj[typeKey].func(); // ✅


  if (obj[typeKey]) {
    obj[typeKey].func(); // ✅
  }
}

for (let key in obj) {
  const typeKey = key as keyof typeof obj;

  obj[typeKey].func(); // ✅


  if (obj[typeKey]) {
    obj[typeKey].func(); // ✅
  }
}

Vladyslav Zubko • Dec 13 '23

Oh, I see.

I understand what issue you're talking about. But here again, the problem is not with noUncheckedIndexedAccess, but with index signatures. If you explicitly annotate all keys, there won't be such an error. Here is the same playground but this explicit keys.

In my article, I repeatedly mentioned that the index signature is a bad thing 😁

Vladyslav Zubko • Dec 13 '23

Agreed!
In general, as always, it depends on the situation 😁

Volodymyr Yepishev • Dec 14 '23

Just dropping my 2 cents, the possible undefined problem of the aforementioned record can be solved by an explicit cast in the value lookup, it's just that both the object and its key need to be casted.

let obj: Record<string, { func: Function }> = {}

for (let key of Object.keys(obj)) {
  (obj[key] as typeof obj[typeof key]).func(); // ✅
}

Though the case seems rather artificial, as you'd probably be using .values or .entries :P

Vladyslav Zubko • Dec 14 '23 • Edited

Hey @bwca !
Thank you for sharing your approach to solving the problem!
I believe it's challenging to assess it solely based on this small code snippet. In real projects, everything can be significantly different 🥲