Search code examples
arraystypescript

Why does array?.length still warn that the array might be undefined?

Given this code:

interface Obj {
  array?: string[]
}

function fuu(obj: Obj) {
  const { array } = obj
  if (array?.length >= 1) {
    // ...
  }
}

Why would it still say 'array.length' is possibly 'undefined'. When the whole purpose of the ? is to check if it's undefined or not.

I'm assuming it's because the operator >= 1 needs a defined value.

Is there a way other than doing:

if (array && array?.length >=1), or const { array = [] } = obj?

Solution

  • The comments are right, the answer is in the question.

    Either if (array && array?.length >=1) or const { array = [] } = obj Are sufficient alternatives.