Regular Expressions For Regular Folk

Advanced Examples

Javascript comments

/\/\*[\s\S]*?\*\/|\/\/.*/g
  • 1 matchconst a = 0; // comment
  • 1 match/* multiline */

[\s\S] is a hack to match any character including newlines. We avoid the dot-all flag because we need to use the ordinary . for single-line comments.

24-Hour Time

/^([01]?[0-9]|2[0-3]):[0-5][0-9](:[0-5][0-9])?$/g
  • 1 match23:59:00
  • 1 match14:00
  • 1 match23:00
  • 0 matches29:00
  • 0 matches32:32

Meta

/<Example source="(.*?)" flags="(.*?)">/gm
  • 1 match<Example source="p[aeiou]t" flags="g">
  • 1 match<Example source="s+$" flags="gm">
  • 1 match<Example source="(['"])(?:(?!\1).)*\1" flags="g">
  • 0 matches<Example source='s+$' flags='gm'>
  • 0 matches</Example>

Replace: <Example regex={/$1/$2}>

I performed this operation in commit d7a684f.

Floating point numbers

  • optional sign
  • optional integer part
  • optional decimal part
  • optional exponent part
/^([+-]?(?=\.\d|\d)(?:\d+)?(?:\.?\d*))(?:[eE]([+-]?\d+))?$/g
  • 1 match987
  • 1 match-8
  • 1 match0.1
  • 1 match2.
  • 1 match.987
  • 1 match+4.0
  • 1 match1.1e+1
  • 1 match1.e+1
  • 1 match1e2
  • 1 match0.2e2
  • 1 match.987e2
  • 1 match+4e-1
  • 1 match-8.e+2
  • 0 matches.

The positive lookahead (?=\.\d|\d) ensures that the regex does not match ..

Latitude and Longitude

/^((-?|\+?)?\d+(\.\d+)?),\s*((-?|\+?)?\d+(\.\d+)?)$/g
  • 1 match30.0260736, -89.9766792
  • 1 match45, 180
  • 1 match-90.000, -180.0
  • 1 match48.858093,2.294694
  • 1 match-3.14, 3.14
  • 1 match045, 180.0
  • 1 match0, 0
  • 0 matches-90., -180.
  • 0 matches.004, .15

See also: Floating Point Numbers

MAC Addresses

/^[a-f0-9]{2}(:[a-f0-9]{2}){5}$/i
  • 1 match01:02:03:04:ab:cd
  • 1 match9E:39:23:85:D8:C2
  • 1 match00:00:00:00:00:00
  • 0 matches1N:VA:L1:DA:DD:R5
  • 0 matches9:3:23:85:D8:C2
  • 0 matchesac::23:85:D8:C2

UUID

/[\da-f]{8}-([\da-f]{4}-){3}[\da-f]{12}/i
  • 1 match123e4567-e89b-12d3-a456-426655440000
  • 1 matchc73bcdcc-2669-4bf6-81d3-e4ae73fb11fd
  • 1 matchC73BCDCC-2669-4Bf6-81d3-E4AE73FB11FD
  • 0 matchesc73bcdcc-2669-4bf6-81d3-e4an73fb11fd
  • 0 matchesc73bcdcc26694bf681d3e4ae73fb11fd

IP Addresses

/\b(?:(?:2(?:[0-4][0-9]|5[0-5])|[0-1]?[0-9]?[0-9])\.){3}(?:(?:2([0-4][0-9]|5[0-5])|[0-1]?[0-9]?[0-9]))\b/g
  • 1 match9.9.9.9
  • 1 match127.0.0.1:8080
  • 1 matchIt's 192.168.1.9
  • 1 match255.193.09.243
  • 1 match123.123.123.123
  • 0 matches123.123.123.256
  • 0 matches0.0.x.0

HSL colours

Integers from 0 to 360

  • 360
  • 300 to 359 — 3, [0-5], any digit
  • 0 to 299
    • optionally 1 or 2 as the hundreds digit
    • optionally any tens digit
    • a units digit
/^0*(?:360|3[0-5]\d|[12]?\d?\d)$/g
  • 1 match360
  • 1 match349
  • 1 match235
  • 1 match152
  • 1 match68
  • 1 match9
  • 0 matches361
  • 0 matches404

Percentages

  • 100, optionally followed by .000…
  • one or two digit integer, optionally followed decimal part
/^(?:100(?:\.0+)?|\d?\d(?:\.\d+)?)%$/g
  • 1 match100%
  • 1 match100.0%
  • 1 match25%
  • 1 match52.32%
  • 1 match9%
  • 1 match0.5%
  • 0 matches100.5%
  • 0 matches42

Bringing it all together

/^hsl\(\s*0*(?:360|3[0-5]\d|[12]?\d?\d)\s*(?:,\s*0*(?:100(?:\.0+)?|\d?\d(?:\.\d+)?)%\s*){2}\)$/gi
  • 1 matchhsl(0,20%,100%)
  • 1 matchHSL(0350, 002%,4.1%)
  • 1 matchhsl(360,10% , 0.2% )