Regular Expressions 101

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Function

  • Match
  • Substitution
  • List
  • Unit Tests (35)

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An explanation of your regex will be automatically generated as you type.
  • 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
  • Non-capturing group
    (?:...)
  • Capturing group
    (...)
  • 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

/
/
mg

Unit Tests

given the string a1_ assert that regex does match
given the string a_1 assert that regex does match
given the string 1a_ assert that regex does match
given the string 1_a assert that regex does match
given the string _a1 assert that regex does match
given the string _1a assert that regex does match
given the string aa11__ assert that regex does match
given the string aa__11 assert that regex does match
given the string 11aa__ assert that regex does match
given the string 11__aa assert that regex does match
given the string __aa11 assert that regex does match
given the string __11aa assert that regex does match
given the string a assert that regex does not match
given the string 1 assert that regex does not match
given the string _ assert that regex does not match
given the string a1 assert that regex does not match
given the string a_ assert that regex does not match
given the string 1a assert that regex does not match
given the string 1_ assert that regex does not match
given the string _a assert that regex does not match
given the string _1 assert that regex does not match
given the string aaa111_ _ assert that regex does match
given the string aaa_ _111 assert that regex does match
given the string 111aaa_ _ assert that regex does match
given the string 111_ _aaa assert that regex does match
given the string _ _aaa111 assert that regex does match
given the string _ _111aaa assert that regex does match
given the string aa11_ assert that regex does not match
given the string 11aa_ assert that regex does not match
given the string _aa11 assert that regex does not match
given the string _11aa assert that regex does not match
given the string a1 assert that regex does not match
given the string 1a assert that regex does not match
given the string a1 assert that regex does not match
given the string 1a assert that regex does not match