This is about a strange behavior IE shows for a regex matching Im trying to do.

Here is a password matching expression Im trying to use for matching the below conditions.

• Must contain minimum 8 to 20 characters, mandatorily including one letter and number
• May include only one of the following special characters: %,&, _, ?, #, =, -
• Cannot have any spaces 
  

^(?=.{0,11}\d)(?=.{0,11}[a-zA-Z])[\w%&?#=-]{8,12}$

  and the javascript to do the match is

 function fnIsPassword(strInput){
  alert("strInput : " + strInput);
  var regExp =/^(?=.{0,11}\d)(?=.{0,11}[a-zA-Z])[\w%&?#=-]{8,12}$/;
  if(strInput.length > 0){
     return (regExp.test(strInput));
  }
  return false;
}

alert(fnIsPassword("1231231")); //false
alert(fnIsPassword("sdfa4gggggg")); //FF: true, false in IE  
alert(fnIsPassword("goog1234#")); //FF: true , false in IE

 

The problem as stated above is that IE gives me false for the last 2 matches.

My IE version is  6.0.2900.5512.xpsp_sp3_gdr.090804-1435 on win XP ; ScriptEngineMajorVersion() = 5 ScriptEngineMinorVersion() = 7.
I got it reproduced on a colleague's machine with the same configuration.

Somehow IE does the {8,12} count constraints after the first digit is matches.
Thus i see that abc45678901 is matched and abc4567890 is not matched ( notice that the counting starts from he first digit match)

Anyone can reproduce this issue ? Any workarounds ? .

Thanks in advance,
mays

http://regexadvice.com/forums/thread/51012.aspx

 

The bug http://regexadvice.com/blogs/mash/archive/2004/10/05/320.aspx

The bug revisited http://regexadvice.com/blogs/mash/archive/2009/02/21/Looking-again-at-the-Lookahead-bug.aspx

 

---

Michael

"In theory, theory and practice are the same. In practice, they are not."
Albert Einstein

Thanks Micheal, I guess the original thread talks about the same animal. :)

I have commented there about this.
Just for the sake of it, here is my final regex , which works in IE and FF. 

 /(?=^[\w%&?#=-]{8,12}$)(?=.+\d)(?=.+[a-zA-Z]).+/