title: Using Material Design Lite API functions in Typescript
body: <p>I'm trying to use the undocumented "Material Design Lite" API and I'm getting a syntax error in Visual Studio of:
  "<strong>Property MaterialCheckbox does not exist on type Element</strong>".
  Do I need a typescript definition file or something? I found a typescript definition file, but it did not help.  I don't even see any property called MaterialCheckbox in the debugger.</p>
  
  <pre><code>document.querySelector('#my_checkbox').MaterialCheckbox.disable();
  </code></pre>