title: Using out of scope functions in Typescript
body: <p>I think this has been addressed somewhere, at some point, just for the life of me I can't remember so here's my question:</p>
  
  <p>I'm doing some javascript work that will be loaded into an existing application. This application has crap loads of functions available and hardly any of it is known to me except some that I want to actually use. So lets say that I know for a fact that window.srslyUsefulFunction will be available to me and I don't care much for porting this in to a typescript definition.</p>
  
  <p>So the question is how do I use window.srslyUsefulFunction in my own typescript file without creating a definition for it?</p>
  
  <p>Example:</p>
  
  <pre><code>class MyClass {
      public MyMethod (id : string) : void {
          // do something 
          var result = window.srslyUsefulFunction(id);
          // do something (with the result)
      }
  }
  </code></pre>