title: Regular Expression For Decimal Value
body: <p>I want a regular expression for decimal input, which can take 4 digits before decimal or comma and 2 digits after decimal/comma. 5 digit number without decimal is invalid. Also can accept null.</p>
  
  <p>Correct Values can be:</p>
  
  <blockquote>
    <p>1, 1111, 2222.56, 0.99, 9999.5 </p>
  </blockquote>
  
  <p>Invalid</p>
  
  <blockquote>
    <p>88888, 8.888,</p>
  </blockquote>
  
  <p>Validation show also include comma along with decimal. </p>
  
  <p>If possible, then also explain the expression.</p>