title: How to "interface" an interface in typescript?
body: <p>I've got a base interface and I want my child interface to look like the base interface.
  How can I do so?</p>
  <pre><code>interface BaseInterface {
    api: { [key: string]: string  };
    ui: { [key: string]: string  };
  }
  
  interface ChildInterface {
    // I want to force this interface to have the same shape as BaseInterface
    // like so :
  
    api: { firstName: string  };
    ui: { firstName: string  };
  }
  </code></pre>
  <p>I tried with <code>type ChildInterface = BaseInterface</code> but I cannot manage to custom my <code>ChildInterface</code> then.</p>
  <p>Thanks</p>