Here are a list of Common Regular Expressions in Javascript.
Note: I will constantly update this post if any common pattern comes into my mind. Any suggestions and comments are very welcome.
Digits
/^[0-9]+$/
Alphabetic Characters
/^[a-zA-Z]+$/
Alpha-Numeric Characters
/^[a-zA-Z0-9]+$/
Date (MM/DD/YYYY)/(MM-DD-YYYY)/(MM.DD.YYYY)/(MM DD YYYY)
/^(0?[1-9]|1[012])[- /.](0?[1-9]|[12][0-9]|3[01])[- /.](19|20)?[0-9]{2}$/
Email Address
/^[a-zA-Z0-9._%-]+@[a-zA-Z0-9.-]+.[a-zA-Z]{2,4}$/
Password
The password must contain one lowercase letter, one uppercase letter, one number, one unique character such as !@#$%^&? and be at least 6 characters long.
/^.*(?=.{6,})(?=.*d)(?=.*[A-Z])(?=.*[a-z])(?=.*[!@#$%^&*? ]).*$/
US Phone Numbers
/^(?([0-9]{3}))?[-. ]?([0-9]{3})[-. ]?([0-9]{4})$/
US Zip code
/^[0-9]{5}(?:-[0-9]{4})?$/
Slug
/^[a-z0-9-]+$/
URL
/((([A-Za-z]{3,9}:(?:\/\/)?)(?:[-;:&=\+\$,\w]+@)?[A-Za-z0-9.-]+|(?:www.|[-;:&=\+\$,\w]+@)[A-Za-z0-9.-]+)((?:\/[\+~%\/.\w-_]*)?\??(?:[-\+=&;%@.\w_]*)#?(?:[\w]*))?)/
IP Address
/^(?:(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?).){3}(?:25[0-5]|2[0-4][0-9]|[01]?[0-9][0-9]?)$/
HTML Tag
/^<([a-z]+)([^<]+)*(?:>(.*)</1>|s+/>)$/
String trimming
/^s*|s*$/g
All the special characters need to be escaped
/[\-\[\]\/\\\{\}\(\)\*\+\?\.\^\$\|]/