TSConfig

strictPropertyInitialization

When set to true, TypeScript will raise an error when a class property was declared but not set in the constructor.

ts
class UserAccount {
  name: string;
  accountType = "user";
 
  email: string;
Property 'email' has no initializer and is not definitely assigned in the constructor.2564Property 'email' has no initializer and is not definitely assigned in the constructor.
  address: string | undefined;
 
  constructor(name: string) {
    this.name = name;
    // Note that this.email is not set
  }
}
Try

In the above case:

  • this.name is set specifically.
  • this.accountType is set by default.
  • this.email is not set and raises an error.
  • this.address is declared as potentially undefined which means it does not have to be set.