Discussion on: The Strictest TypeScript Config

[Vladyslav Zubko]

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(); // ✅
  }
}

[Yeom suyun]

The solution you provided might not resolve the issue.
TS Playground

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

for (let key of Object.keys(obj)) {
  const value = obj[key]
  if (value) {
    value.func();
  }
}

for (let key in obj) {
  const value = obj[key] as { func: Function }
  value.func();
}

[Vladyslav Zubko]

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 😁

[Yeom suyun]

Yes, indeed.
If you have been using the strict option in TypeScript, applying additional stricter options may not introduce many new errors.
However, for types like Array or Record, there are clear use cases, and it's not accurate to categorize them as inherently bad.
For instance, I found type casting cumbersome in cases like the code below to eliminate errors.

/**
 * @param {string} text
 * @returns {string}
 */
let _default = text => {
  let regex = ""
  let len = text.length - 1
  for (let i = 0; i < len; i++) {
    let t = /** @type {string} */(text[i])/**/
    regex += first_consonant_letters[t] ?? get_letter_range(t)
  }
  return regex + get_letter_range(
    /** @type {string} */(text[len])/**/
  )
}

[Vladyslav Zubko]

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

[Volodymyr Yepishev]

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]

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 🥲