Typescript empty object for a typed variable

Question

Say I have:

type User = {
...
}

I want to create a new user but set it to be an empty object:

const user: User         


        

Answer 1

Note that using const user = {} as UserType just provides intellisense but at runtime user is empty object {} and has no property inside. that means user.Email will give undefined instead of ""

type UserType = {
    Username: string;
    Email: string;
}

So, use class with constructor for actually creating objects with default properties.

type UserType = {
  Username: string;
  Email: string;
};

class User implements UserType {
  constructor() {
    this.Username = "";
    this.Email = "";
  }

  Username: string;
  Email: string;
}

const myUser = new User();
console.log(myUser); // output: {Username: "", Email: ""}
console.log("val: "+myUser.Email); // output: ""

You can also use interface instead of type

interface UserType {
  Username: string;
  Email: string;
};

...and rest of code remains same.

---

Actually, you can even skip the constructor part and use it like this:

class User implements UserType {
      Username = ""; // will be added to new obj
      Email: string; // will not be added
}

const myUser = new User();
console.log(myUser); // output: {Username: ""}