Monday, March 14, 2011

Regular Expressions

I'm sure most of you from the programming world are familiar with regular expressions. For most of you that are from the programming world and aren't familiar with them - you should be ashamed of yourselves. I'm only this haughty because I only figured out how to use regular expressions LAST NIGHT. Can you believe that? In the middle of a large project where the deadline looms among the next sunrise and validation on a HUGE form is key, I learned to master the use of ye ole RegEx... But not without a large amount of help, though. I really have to give credit to the guys over at GSkinner.com for their RegExr tool. With this tool, I was able to turn my email address validation code from this :
function echeck(str) {

  var at="@"
  var dot="."
  var lat=str.indexOf(at)
  var lstr=str.length
  var ldot=str.indexOf(dot)
  if (str.indexOf(at)==-1){
     alert("Invalid E-mail ID")
     return false
  }

  if (str.indexOf(at)==-1 || str.indexOf(at)==0 || str.indexOf(at)==lstr){
     alert("Invalid E-mail ID")
     return false
  }

  if (str.indexOf(dot)==-1 || str.indexOf(dot)==0 || str.indexOf(dot)==lstr){
      alert("Invalid E-mail ID")
      return false
  }

   if (str.indexOf(at,(lat+1))!=-1){
      alert("Invalid E-mail ID")
      return false
   }

   if (str.substring(lat-1,lat)==dot || str.substring(lat+1,lat+2)==dot){
      alert("Invalid E-mail ID")
      return false
   }

   if (str.indexOf(dot,(lat+2))==-1){
      alert("Invalid E-mail ID")
      return false
   }
  
   if (str.indexOf(" ")!=-1){
      alert("Invalid E-mail ID")
      return false
   }

    return true     
 }

function ValidateForm(){
 var emailID=document.frmSample.txtEmail
 
 if ((emailID.value==null)||(emailID.value=="")){
  alert("Please Enter your Email ID")
  emailID.focus()
  return false
 }
 if (echeck(emailID.value)==false){
  emailID.value=""
  emailID.focus()
  return false
 }
 return true
 }
 
 
To this :
function validateEmail(str) {
  var RE_EMAIL = /^[a-z]+[\w-_]+@[a-z]+\.[^@]*\w\w$/
  if(RE_EMAIL.test(str)) {
    return true;
  }
  else {
    return false;
  }
}
If you are like me and you never understood regular expressions, I would advise you give them a try. If you're a web developer, one of these days you are going to have to develop a form component that needs validation. Learning regular expressions is a definite time saver and I would suggest you invest the necessary time into learning them.
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