if (window?.sessionStorage?.getItem('accessToken')?.length > 0) {
  this.navigateToApplication();
}

getting an error as :

Object is possibly 'undefined'.ts(2532)

how to fix this? I am trying to get the value by optional here.

CodePudding user response：

This could use a better error message. :-) The problem is that since window?.sessionStorage?.getItem('accessToken')? evaluates to undefined if the item isn't there, your if comparison is undefined | number > number, which is problematic from a type perspective.

You can just get rid of the > 0 since both undefined and 0 are falsy:

if (window?.sessionStorage?.getItem('accessToken')?.length) {
// −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−^−−− Removed `> 0`
    this.navigateToApplication();
}

Playground link

Alternatively, provide a default value using nullish coalescing (??):

if (window?.sessionStorage?.getItem('accessToken')?.length ?? 0 > 0) {
// −−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−−^^^^^
    this.navigateToApplication();
}

window?.sessionStorage?.getItem('accessToken')?.length ?? 0 will evaluate to 0 if the item isn't there, which makes for a number > number comparison, which TypeScript is happy with.

Playground link

CodePudding user response：

The problem here is that window.sessionStorage.getItem("accessToken") might be undefined. That's why you need to check beforehand if your item exists.

  const accessToken = window.sessionStorage.getItem("accessToken");
  if (accessToken && accessToken?.length > 0) {
    this.navigateToApplication();
  }