namespace

namespace Home {
  class Header {
    constructor() {
      const elem = document.createElement('div');
      elem.innerText = "this is header";
      document.body.appendChild(elem);
    }
  }
  class Content {
    constructor() {
      const elem = document.createElement('div');
      elem.innerText = "this is content";
      document.body.appendChild(elem);
    }
  }
  class Footer {
    constructor() {
      const elem = document.createElement('div');
      elem.innerText = "this is footer";
      document.body.appendChild(elem);
    }
  }
  export class Page {
    constructor() {
      new Header();
      new Content();
      new Footer();
    }
  }
}
new Home.Page(); 
// ts编译后会有4个全局变量 Header、Content、Footer、Page
// 加上命名空间后，只有一个 Home 全局变量