Typescript - Tips & Tricks - Non-null assertion operator

In some cases, you have a field that you initialize in a method, and if you follow the flow of the code you are sure that this field is initialized but typescript doesn’t understand it. An example

type Person = {
  name: string;
};

let person: Person;

function initialize() {
  person = { name: "name" };
}

initialize();
console.log("Hello", person.name); // Variable 'person' is used before being assigned.

In this case, you can see how the typescript compiler doesn’t understand that the “person” field isn’t null but it’s initialized. To resolve this problem, the typescript language exposes us the “Non-null assertion operation”(!). This operator says to the compiler that the field isn’t null or undefined but it’s defined. The previous example can be reviewed in this way

type Person = {
  name: string;
};

let person: Person;

function initialize() {
  person = { name: "name" };
}

initialize();
console.log("Hello", person!.name);

As you can see, in this case, the code doesn’t have errors and the compilation ends with success.

That’s all for today! Bye-bye guys!