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
  • 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

/
/
gmsx

Test String

Code Generator

Generated Code

const regex = / # begin capture group 1 \{\s+"name":[ ]" # match '{' then 1+ whitespace chars, then '"name": " (\w+) # match 1+ word chars, save to capture group 1 - # match '-' (\w+) # match 1+ word chars, save to capture group 2 - # match '-' (\w+) # match 1+ word chars, save to capture group 3 - # match '-' (\w+) # match 1+ word chars, save to capture group 4 ( # begin capture group 5 ",\s+"units":[ ] # match '",', then 1+ whitespaces then '"units": ' "\w+" # match 1+ word chars ,\s+"value":[ ] # match ',', then 1+ whitespaces then '"value": ' \d+ # match 1+ digits \s+\} # match 1+ whitespaces then '"units": ' ) # end capture group 5 # end capture group 1 (?! # begin negative lookahead .* # match 0+ chars \{\s+"name":[ ]" # match '{' then 1+ whitespace chars then '"name": ' then '"' \1_ # match contents of capture group 1 then '_' \2_ # match contents of capture group 2 then '_' \3_ # match contents of capture group 3 then '_' \4 # match contents of capture group 4 \5 # match contents of capture group 5 ) # end of negative lookahead | # or \{\s+"name":[ ]" # match '{' then 1+ whitespace chars, then '"name": " \w+ # match 1+ word chars _ # match '_' \w+ # match 1+ word chars _ # match '_' \w+ # match 1+ word chars _ # match '_' \w+ # match 1+ word chars (?5) # execute code constructing capture group 6 /gms; // Alternative syntax using RegExp constructor // const regex = new RegExp(' # begin capture group 1 \\{\\s+"name":[ ]" # match \'{\' then 1+ whitespace chars, then \'"name": " (\\w+) # match 1+ word chars, save to capture group 1 - # match \'-\' (\\w+) # match 1+ word chars, save to capture group 2 - # match \'-\' (\\w+) # match 1+ word chars, save to capture group 3 - # match \'-\' (\\w+) # match 1+ word chars, save to capture group 4 ( # begin capture group 5 ",\\s+"units":[ ] # match \'",\', then 1+ whitespaces then \'"units": \' "\\w+" # match 1+ word chars ,\\s+"value":[ ] # match \',\', then 1+ whitespaces then \'"value": \' \\d+ # match 1+ digits \\s+\\} # match 1+ whitespaces then \'"units": \' ) # end capture group 5 # end capture group 1 (?! # begin negative lookahead .* # match 0+ chars \\{\\s+"name":[ ]" # match \'{\' then 1+ whitespace chars then \'"name": \' then \'"\' \\1_ # match contents of capture group 1 then \'_\' \\2_ # match contents of capture group 2 then \'_\' \\3_ # match contents of capture group 3 then \'_\' \\4 # match contents of capture group 4 \\5 # match contents of capture group 5 ) # end of negative lookahead | # or \\{\\s+"name":[ ]" # match \'{\' then 1+ whitespace chars, then \'"name": " \\w+ # match 1+ word chars _ # match \'_\' \\w+ # match 1+ word chars _ # match \'_\' \\w+ # match 1+ word chars _ # match \'_\' \\w+ # match 1+ word chars (?5) # execute code constructing capture group 6 ', 'gms') const str = `{ "body": { "metricsArray": [ { "name": "free-aa-bb2-123x123Profiles", "units": "profiles", "value": 14 }, { "name": "free_aa_bb2_123x123Profiles", "units": "profiles", "value": 14 } ], "name": "regionxxx", "timeStamp": "2022-01-20T04:58:29.875Z" } } `; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; let m; while ((m = regex.exec(str)) !== null) { // This is necessary to avoid infinite loops with zero-width matches if (m.index === regex.lastIndex) { regex.lastIndex++; } // 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