Answers for "has no initializer and is not definitely assigned in the constructor"

Property 'firstName' has no initializer and is not definitely assigned in the constructor

"angularCompilerOptions": {
    //   ...
    "strictPropertyInitialization": false
    //   ...
  }

Property has no initializer and is not definitely assigned in the constructor

@Component({...})
export class Component {
  @Input() myInput: string|undefined;
}

OR

@Component({...})
export class Component {
  @Input() myInput!: string;
}