Regex password validation in javascript

In this first example, the password must be at least 8 characters long and start and end with a letter. 

var re = /^[A-Za-z]\w{6,}[A-Za-z]$/;
if (!re.test(myString)) { alert("Please enter a valid password!"); }




In this second example, the password length doesn't matter, but the password must contain at least 1 number, at least 1 lower case letter, and at least 1 upper case letter. 

var re = /^\w*(?=\w*\d)(?=\w*[a-z])(?=\w*[A-Z])\w*$/
if (!re.test(myString)) { alert("Please enter a valid password!"); }




Password Regular Expression Pattern is as follows:

((?=.*\d)(?=.*[a-z])(?=.*[A-Z])(?=.*[@#$%]).{6,20})

Explanation : (   # Start of group

(?=.*\d)  #   must contains one digit from 0-9
  (?=.*[a-z])  #   must contains one lowercase characters
  (?=.*[A-Z])  #   must contains one uppercase characters
  (?=.*[@#$%])  #   must contains one special symbols in the list "@#$%"
              .  #     match anything with previous condition checking
                {6,20} #        length at least 6 characters and maximum of 20 
)   # End of group

?= – means apply the assertion condition, meaningless by itself, always work with other combination

Tags : regex validation, javascript, regex