title: How do I check if a JavaScript parameter is a number?
body: <p>I'm doing some trouble-shooting and want to add a check that a parameter to a function is a number. How do I do this?</p>
  
  <p>Something like this...</p>
  
  <pre><code>function fn(id) {
      return // true iff id is a number else false
  }
  </code></pre>
  
  <p>Even better is if I can check that the parameter is a number AND a valid integer.</p>