Regular Expressions provide a very powerful and easy method of client side validation. They are also both supported by IE and Netscape. It takes a lot less code, and works on every browser. Here’s a simple date validation in Javascript?using regular expressions.

 function validateDate(input){  var datePattern = /^(d{2})/(d{2})/(d{4})$/;  if(!datePattern.test(input))  {    alert("Error... please enter date in mm/dd/yyyy format");    return false;  }  var month = parseInt(RegExp.$1);  if(month <=0 || month > 12)  {    alert("Error.. invalid month");    return false;  }  var year = parseInt(RegExp.$3);  var daysArray = new Array(31,28,31,30,31,30,31,31,30,31,30,31);  if(year % 4 == 0)  {    daysArray[1] = 29;  }  var date = parseInt(RegExp.$2);  if(date <=0 || date > daysArray[month-1])  {    alert("Error... invalid date");    return false;  }  return true;}