Is there a way to specify to a JavaScript variable that it must have a defined value upon creation?

getPersonneById(id: number): Personne{
    const personne = this.personnes.find( personne => {
      return personne.id == id;
    });
    return personne;
}

An error message is displayed: Unable to assign type 'Person | undefined' to type 'Person'. Unable to assign type 'undefined' to type 'Person'.

I have also tried the following workaround, although it is not ideal:

getPersonneById(id: number): Personne{
    const personne = this.personnes.find( personne => {
      return personne.id == id;
    });
    if(typeof personne !== 'undefined'){
      return personne;
    }else{
      return this.personnes['0'];
    }
}

The variable 'personnes' is an array.

My question is whether there is a way to ensure that the variable cannot be undefined or if there is a better solution.

Answer №1

If you are confident that a value will always be found using the find method, you can signal this guarantee in TypeScript by using the non-null assertion operator:

return personne!;

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