A class decorator function

class-decorator-function-example

/*
A class decorator function will receive target class UserRef, which is User in above example (on which decorator is applied)
and must return a constructor function. This opens the door of infinite possibilities that you can do with the decorator.
Hence class decorators are more popular than method/property decorators
*/

Ref: https://itnext.io/a-minimal-guide-to-ecmascript-decorators-55b70338215e

function withLoginStatus( UserRef ) {
    return class extends UserRef {
        constructor( ...args ) {
            super( ...args );
            this.isLoggedIn = false;
        }
        setLoggedIn() {
            this.isLoggedIn = true;
        }
    }
}
@withLoginStatus
class User {
    constructor( firstName, lastName ) {
        this.firstName = firstName;
        this.lastName = lastName;
    }
}
let user = new User( 'John', 'Doe' );
console.log( 'Before ===> ', user );
// set logged in
user.setLoggedIn();
console.log( 'After ===> ', user );