The data type 'string | boolean | null' cannot be assigned to type 'boolean'. Specifically, the type 'null' cannot be assigned to type 'boolean'

Can you spot the issue in this code snippet?

isAuthenticated(): boolean
  {
    var token = localStorage.getItem(ACCESS_TOKEN_KEY);
    return token && !this.jwtHelper.isTokenExpired(token);
  }

Error:

The variable is returning a type of 'string | boolean | null', which cannot be directly assigned to type 'boolean'.
   Also, the error shows that 'null' is being wrongly assigned as 'boolean'.

Answer №1

To obtain a boolean result, it is necessary to convert the variables into boolean values. Here's an example:

isAuthenticated(): boolean
{
  var token = localStorage.getItem(ACCESS_TOKEN_KEY);
  return !!token && !!this.jwtHelper.isTokenExpired(token);
}

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