Regular Expressions 101

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An explanation of your regex will be automatically generated as you type.
Detailed match information will be displayed here automatically.
  • All Tokens
  • Common Tokens
  • General Tokens
  • Anchors
  • Meta Sequences
  • Quantifiers
  • Group Constructs
  • Character Classes
  • Flags/Modifiers
  • Substitution
  • A single character of: a, b or c
    [abc]
  • A character except: a, b or c
    [^abc]
  • A character in the range: a-z
    [a-z]
  • A character not in the range: a-z
    [^a-z]
  • A character in the range: a-z or A-Z
    [a-zA-Z]
  • Any single character
    .
  • Alternate - match either a or b
    a|b
  • Any whitespace character
    \s
  • Any non-whitespace character
    \S
  • Any digit
    \d
  • Any non-digit
    \D
  • Any word character
    \w
  • Any non-word character
    \W
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • Zero or one of a
    a?
  • Zero or more of a
    a*
  • One or more of a
    a+
  • Exactly 3 of a
    a{3}
  • 3 or more of a
    a{3,}
  • Between 3 and 6 of a
    a{3,6}
  • Start of string
    ^
  • End of string
    $
  • A word boundary
    \b
  • Non-word boundary
    \B

Regular Expression
No Match

/
/

Test String

Code Generator

Language

Generated Code

const regex = /[^/]*$/; // Alternative syntax using RegExp constructor // const regex = new RegExp('[^\/]*$', '') const str = `# coding=utf8 # the above tag defines encoding for this document and is for Python 2.x compatibility import re regex = r"(?<=\\D|^)(?<year>\\d{4})(?<sep>[^\\w\\s])(?<month>1[0-2]|0[1-9])\\k<sep>(?<day>0[1-9]|[12][0-9]|(?<=11\\k<sep>|[^1][4-9]\\k<sep>)30|(?<=1[02]\\k<sep>|[^1][13578]\\k<sep>)3[01])(?=\\D|\$)" test_str = ("\\n" "2020-01-01\\n" "2020-01-31\\n" "2020-02-29\\n" "2020-03-31\\n" "2020-04-30\\n" "2020-05-31\\n" "2020-06-30\\n" "2020-07-31\\n" "2020-08-31\\n" "2020-09-30\\n" "2020-10-31\\n" "2020-11-30\\n" "2020-12-31\\n" "2020-01-01 00:00:00,000\\n" "2020-01-01_00:00:00,000\\n" "2020-01-01-00:00:00,000\\n" "2020-01-01T00:00:00,000\\n" "2222-01-01\\n" "2222/11/22\\n" "2222.11.22\\n\\n" "// Invalid dates\\n" "2020-00-01\\n" "2020-01-00\\n" "000-01-01\\n" "222-01-01\\n" "2020-1-1\\n" "2020-1-01\\n" "2020-01-1\\n" "2020-22-01\\n" "2020-01-33\\n" "2020-01-32\\n" "2020-02-30\\n" "2020-03-32\\n" "2020-04-31\\n" "2020-05-32\\n" "2020-06-31\\n" "2020-07-32\\n" "2020-08-32\\n" "2020-09-31\\n" "2020-10-32\\n" "2020-11-31\\n" "2020-12-32\\n" "a222-01-01\\n" "2a22-01-01\\n" "22a2-01-01\\n" "222a-01-01\\n" "2222-a1-01\\n" "2222-0a-01\\n" "2222-1a-01\\n" "2222-01-a1\\n" "2222-01-0a\\n" "2222-01-1a\\n" "2222-11.22\\n" "2222z11z22\\n" "2222811822") matches = re.finditer(regex, test_str, re.MULTILINE) for matchNum, match in enumerate(matches, start=1): print ("Match {matchNum} was found at {start}-{end}: {match}".format(matchNum = matchNum, start = match.start(), end = match.end(), match = match.group())) for groupNum in range(0, len(match.groups())): groupNum = groupNum + 1 print ("Group {groupNum} found at {start}-{end}: {group}".format(groupNum = groupNum, start = match.start(groupNum), end = match.end(groupNum), group = match.group(groupNum))) # Note: for Python 2.7 compatibility, use ur"" to prefix the regex and u"" to prefix the test string and substitution. `; let m; if ((m = regex.exec(str)) !== null) { // The result can be accessed through the `m`-variable. m.forEach((match, groupIndex) => { console.log(`Found match, group ${groupIndex}: ${match}`); }); }

Please keep in mind that these code samples are automatically generated and are not guaranteed to work. If you find any syntax errors, feel free to submit a bug report. For a full regex reference for JavaScript, please visit: https://developer.mozilla.org/en/docs/Web/JavaScript/Guide/Regular_Expressions