tsbundle/test/ts_web/index.ts

const myConst: string = 'hello';

function sealed(constructor: Function) {
  Object.seal(constructor);
  Object.seal(constructor.prototype);
}

@sealed
class BugReport {
  type = 'report';
  title: string;

  constructor(t: string) {
    this.title = t;
  }
}

console.log(myConst);