You can use regular expressions with many languages or tools, including Python and JavaScript.
Regex to Validate a Username
Consider a username that is only valid if it satisfies the following conditions:
The number of characters must be between 5 and 15. (You may specify a different range according to your requirements, but do make changes in the regex accordingly. ) The string should only contain alphanumeric characters and/or underscores (_). The first character of the string should be alphabetic.
The following regex satisfies the above conditions and can validate a username:
If you are not comfortable with the above expression, check out a beginner’s guide to regular expressions first. This is a Python approach to validate a username:
Running this code will confirm that the first username is valid but the second isn’t:
Similarly, you can validate a username in JavaScript using the following code:
You can use this code to validate HTML forms using regular expressions.
Regex to Validate an Email Address
The regex to validate an email address is not perfect. There’s no universally agreed-upon regex to validate an email address. It completely boils down to your definition of valid.
Below is a list of conditions that can validate most email addresses:
The username should only contain alphanumeric, underscore, dash, and/or dot characters. The email id string must have one @ character. The domain name should only contain alphanumeric, underscore, or dash characters. There must be a dot after the domain name. The domain extension should only contain alphanumeric, underscore, or dash characters. The domain extension length should be between 2 and 4.
The following regex satisfies the above conditions and can validate an email address:
This is a Python approach to validating an email address:
Again, the output confirms the first email address is valid while the second is invalid:
You can validate an email in JavaScript using the following code:
Check Password Strength Using Regular Expressions
Strong passwords are essential from a security perspective. You need to make sure that end users have strong enough passwords so that others cannot access their accounts.
The following rules make sure that the password strength of your application is strong:
The minimum number of characters must be 8. The string must have at least one digit. The string must have at least one uppercase character. The string must have at least one lowercase character. The string must have at least one special character.
The following regex satisfies the above conditions and can help ensure a stronger password:
You can check password strength in Python using the following code:
Running this code will confirm that the first password is strong while the second one is weak:
You can check the password strength in JavaScript using the following code:
Regular Expression to Match a Valid Date
If you want to quickly check whether the given dates are in the traditional date format or not, you can do so using regex.
The following regular expression matches a date in mm/dd/yyyy format:
The following Python code validates the date is in mm/dd/yyyy format:
Once more, the output confirms the first date format is valid, but the second is invalid:
You can validate the date in mm/dd/yyyy format in JavaScript using the following code:
Empty String Validation Using Regular Expressions
You can check if a string is empty using the following regular expression:
Below is the Python approach for empty string validation:
The following output demonstrates that the first given string is empty while the second isn’t:
Use the following JavaScript code to check if the string is empty or not:
RegEx to Validate ZIP Code (US Postal Code)
You can validate a ZIP code (U.S. Postal Code) in both the five-digit and nine-digit (called ZIP+4) formats using the following regular expression:
Below is the Python code to validate ZIP codes:
Running this code will confirm that the first and second ZIP codes are valid but the third isn’t:
Use the following JavaScript code to validate the ZIP code using regex:
Verify User Input With Robust Code
You learned how to validate user account details using regular expressions. Validating these details makes the code robust and helps to tackle security issues and unwanted bugs. Robust code provides a safe and secure experience for your users.
You should make sure you are validating the input data either on the client side or the server side to be always on the safe side from hackers.
