title: Validate decimal numbers in JavaScript - IsNumeric()
body: <p>What's the cleanest, most effective way to validate decimal numbers in JavaScript?</p>
  
  <p>Bonus points for:</p>
  
  <ol>
  <li>Clarity. Solution should be clean and simple.</li>
  <li>Cross-platform.</li>
  </ol>
  
  <p>Test cases:</p>
  
  <pre><code>01. IsNumeric('-1')      =&gt; true
  02. IsNumeric('-1.5')    =&gt; true
  03. IsNumeric('0')       =&gt; true
  04. IsNumeric('0.42')    =&gt; true
  05. IsNumeric('.42')     =&gt; true
  06. IsNumeric('99,999')  =&gt; false
  07. IsNumeric('0x89f')   =&gt; false
  08. IsNumeric('#abcdef') =&gt; false
  09. IsNumeric('1.2.3')   =&gt; false
  10. IsNumeric('')        =&gt; false
  11. IsNumeric('blah')    =&gt; false
  </code></pre>