title: Check if a variable contains a numerical value in Javascript?
body: <p>In PHP, it's pretty easy:</p>
  
  <pre><code>is_numeric(23);//true
  is_numeric("23");//true
  is_numeric(23.5);//true
  is_numeric(true);//false
  </code></pre>
  
  <p>But how do I do this in Javascript?
  I could use a regular expression, but is there a function for this?</p>