Essential Regex Cheat Sheet: 20 Common Validation Patterns for Developers

1. Date format validation (JavaScript)

Validate a basic date format using a regular expression and alert on error.

var reg = /^(\d{1,4})(-|\/)(\d{1,2})\2(\d{1,2})$/;
var r = fieldValue.match(reg);
if (r == null) alert('Date format error!');

2. Password strength

The password must contain digits, lowercase and uppercase letters, be 8‑10 characters long, and exclude special symbols.

^(?=.*\d)(?=.*[a-z])(?=.*[A-Z]).{8,10}$

3. Chinese characters only

Ensures the entire string consists of Chinese characters.

^[\u4e00-\u9fa5]{0,}$

4. Alphanumeric or underscore

Matches strings composed of letters, digits, or underscores.

^\w+$

5. Email address

Comprehensive pattern for validating standard email formats.

[\w!#$%&'*+/=?^_`{|}~-]+(?:\.[\w!#$%&'*+/=?^_`{|}~-]+)*@(?:[\w](?:[\w-]*[\w])?\.)+[\w](?:[\w-]*[\w])?

6. 15‑digit ID number

^[1-9]\d{7}((0\d)|(1[0-2]))(([0|1|2]\d)|3[0-1])\d{3}$

7. 18‑digit ID number

^[1-9]\d{5}[1-9]\d{3}((0\d)|(1[0-2]))(([0|1|2]\d)|3[0-1])\d{3}([0-9]|X)$

8. Full date validation (yyyy‑mm‑dd, leap year aware)

^(?:(?!0000)[0-9]{4}-(?:(?:0[1-9]|1[0-2])-(?:0[1-9]|1[0-9]|2[0-8])|(?:0[13-9]|1[0-2])-(?:29|30)|(?:0[13578]|1[02])-31)|(?:[0-9]{2}(?:0[48]|[2468][048]|[13579][26])|(?:0[48]|[2468][048]|[13579][26])00)-02-29)$

9. Monetary amount (up to two decimal places)

^[0-9]+(\.[0-9]{2})?$

10. Mobile phone number (China)

^(13[0-9]|14[5|7]|15[0|1|2|3|5|6|7|8|9]|18[0|1|2|3|5|6|7|8|9])\d{8}$

11. IPv4 address

\b(?:(?: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]?)\b

12. IPv6 address

(([0-9a-fA-F]{1,4}:){7,7}[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,4}:){1,7}:|([0-9a-fA-F]{1,4}:){1,6}:[0-9a-fA-F]{1,4}|([0-9a-fA-F]{1,5}(:[0-9a-fA-F]{1,4}){1,2})|([0-9a-fA-F]{1,4}:){1,4}(:[0-9a-fA-F]{1,4}){1,3}|([0-9a-fA-F]{1,3}(:[0-9a-fA-F]{1,4}){1,4})|([0-9a-fA-F]{1,2}(:[0-9a-fA-F]{1,4}){1,5})|([0-9a-fA-F]{1}:((:[0-9a-fA-F]{1,4}){1,6})|:((:[0-9a-fA-F]{1,4}){1,7}|:)|fe80:(:[0-9a-fA-F]{0,4}){0,4}%[0-9a-zA-Z]{1,}|::(ffff(:0{1,4}){0,1}:){0,1}((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])|([0-9a-fA-F]{1,4}:){1,4}:((25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9])\.){3,3}(25[0-5]|(2[0-4]|1{0,1}[0-9]){0,1}[0-9]))

13. Ensure URL has protocol prefix

if (!s.match(/^[a-zA-Z]+:\/\//)) { s = 'http://' + s; }

14. Extract URL

^(f|ht){1}(tp|tps):\/\/([\w-]+\.)+[\w-]+(\/[\w- ./?%&=]*)?

15. File path and .txt extension

^([a-zA-Z]\:|\\)\\([^\\]+\\)*[^\/:*?"<>|]+\.txt(l)?$

16. Color hex code

^#([A-Fa-f0-9]{6}|[A-Fa-f0-9]{3})$

17. Extract image source URL

\< *[img][^>]*[src] *= *["']{0,1}([^"' >]*)

18. Extract hyperlink (excluding certain domains)

(<a\s*(?!.*\brel=)[^>]*)(href="https?:\/\/)((?!(?:(?:www\.)?'.implode('|(?:www\.)?', $follow_list).'))[^"]+)("((?!.*\brel=)[^>]*)(?:[^>]*)>)

19. CSS property declaration

^\s*[a-zA-Z\-]+\s*[:]{1}\s[a-zA-Z0-9\s.#]+[;]{1}

20. HTML comment

<!--(.*?)-->

21. Match any HTML tag

<\/?\w+((\s+\w+(\s*=\s*(?:".*?"|'.*?'|[^'"&>\s]+))?)+\s*|\s*)\/?>

The cheat sheet concludes with an illustrative image and attribution to the original author.