title: how to use rxjs isNumeric() function?
body: <p>I'm new to rxjs but I think it's part of all ng apps and I've read that it has a handy isNumeric() function.  I tried both of the following imports:</p>
  
  <pre><code>import 'rxjs/util/isNumeric';
  import 'es6/util/isNumeric';
  </code></pre>
  
  <p>Here's some sample code that I tried to hook into this rxjs isNumeric() function:</p>
  
  <pre><code>var testString = "100";
  
  //this doesn't compile
  var isNumber = isNumeric(testString);
  
  //this fails at runtime
  var isNumber = testString.isNumeric();
  </code></pre>
  
  <p>What am I missing with this?</p>