title: String or Number values in Typescript
body: <p>An example of what I am trying to achieve:</p>
  
  <pre><code>class Test {
      private _folderId: number;
      private _pageId: number;
      private _folderName: string;
      private _pageName: string;
  
      constructor(pageId: string | number, folderId: string | number){
          this._folderId = (!isNaN(+folderId)) ? folderId : undefined;
          this._pageId = (!isNaN(+pageId)) ? pageId : undefined;
          this._folderName = (isNaN(+folderId)) ? folderId : undefined;
          this._pageName = (isNaN(+pageId)) ? pageId : undefined;
      }
  }
  </code></pre>
  
  <p>Unfortunately this throws compiler error: </p>
  
  <pre><code>TS2322:Type 'string | number' is not assignable to type 'number'. Type 'string' is not assignable to type 'number'.
  </code></pre>
  
  <p>and so on (similar error for each var).</p>
  
  <p>Is there any way around it? At the moment only thing I can do is to set page and folder id to type any...</p>