Regular Expressions 101

Community Patterns

1

Date - Extract & Validate - Fully tested - Format YYYY-MM-DD (dynamic parts separator / can use a different separator)

Created·2020-11-20 19:31
Flavor·JavaScript
A fully tested regex that extracts and validates date parts using named capturing groups. \ Validations: Year must be preceded by nothing or a non-digit character Year must have 4 digits Month must be between 01 and 12 Month must have 2 digits Day must be between 01 and the maximum number of days for the month (e.g. february can't have more than 29 days) Day must have 2 digits Day must be followed by nothing or a non-digit character Separator must be any single character that is not a space or an alphanumeric character Separator must be the same between each date part \ Capturing groups: | # | Name | Description | |:-:|:-------:|-------------------------------------| | 1 | year | 4 digits of the year | | 2 | sep | Date parts separator | | 3 | month | 2 digits of the month | | 4 | day | 2 digits of the date (day of month) | \ Example usage: let match = regex.exec('2020-11-22') console.log('year: %s, month: %s, day: %s', match.groups.year, match.groups.month, match.groups.day) // year: 2020, month: 11, day: 22 \ Compatibility: (updated 2020-11-20) Chrome >= 64 Edge >= 79 Firefox >= 78 IE incompatible (lookbehind assertions & named capture groups not supported) Opera >= 51 Safari incompatible (lookbehind assertions not supported) NodeJS >= 10.0.0 See regex compatibility table. \ Note: does not validate leap years (not really possible in regex)
Submitted by Elie Grenon (DrunkenPoney) <elie.grenon.1@gmail.com>

Community Library Entry

1

Regular Expression
Created·2024-06-21 08:22
Flavor·PCRE2 (PHP)

/
^(?!.*@.*@)(?!.*\.\.)(^[a-zA-Z0-9._%+-]{1,64}@)([a-zA-Z0-9.-]+\.[a-zA-Z]{2,}(?:\.[a-zA-Z]{2,255})?)$
/
gm
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Description

Email validation

Explanation

  1. ^(?!.@.@) Asserts that the string does not contain two consecutive “@” symbols.

  2. ** (?!.*..)**
    Ensures that there are no consecutive periods (“.”) in the string.

  3. ^[a-zA-Z0-9._%+-]{1,64}@ Matches an email address with a maximum length of 64 characters before the “@” symbol. It allows alphanumeric characters, dots, underscores, percent signs, plus signs, and hyphens.

  4. ([a-zA-Z0-9.-]+.[a-zA-Z]{2,}(?:.[a-zA-Z]{2,255})?)$
    Captures the domain part of the email address. It allows alphanumeric characters, dots, and hyphens.

  5. (?:.[a-zA-Z]{2,255})? This group allows for optional subdomains (e.g., “.foo.bar”).

Includes

  • valid local part
  • Hostpart
  • valid TLD
  • optional SLD
  • unique @
  • No double dots > ..

If you have any improvements or issues: Cxbersxnic - Github

Submitted by Cxbersxnic