title: javascript email regular expression
body: <p>Can someone explain this regular expression to validate email.</p>
  
  <pre><code>var emailExp = /^[\w\-\.\+]+\@[a-zA-Z0-9\.\-]+\.[a-zA-z0-9]{2,4}$/;
  </code></pre>
  
  <p>I need to know what does this independent elements do</p>
  
  <pre><code>"/^"  and "\"  and "\.\-" and "$"  //Please explain individually
  </code></pre>
  
  <p>Thanks in advance  </p>