regular expression for validating password field

Question

I am a learner in java script currently I am going through the regular expression for validating the password field, I want my password field to contain characters and only one number in any place of the string,

I tried the following regular expression it checks for at-least one number and one character in the string

^[A-Za-z0-9 _]*[A-Za-z0-9][A-Za-z0-9 _]*$

Can anyone help me!

Answer 1

All you need is adding a lookahead at the start:

^(?=\D*\d\D*$)[A-Za-z0-9 _]*[A-Za-z0-9][A-Za-z0-9 _]*$

The lookahead makes sure there is zero or more nondigits followed by a digit and zero or more nondigits up to the end of string.

Answer 2

Use this RE

(?!^[0-9] $)(?!^[a-zA-Z] $)^([a-zA-Z0-9]{6,15})$

Answer 3

A simpler expression would be

^\D*\d\D*$

where the meaning is

• Zero or more non-numbers
• A number
• Zero or more non-numbers

If you want at least another character...

^(\D+\d\D*)|(\D*\d\D+)$

where the two provided alternatives require either before or after at least one non-digit.