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
No Match

/
/
gm

Test String

Code Generator

Language

Generated Code

const regex = /^\s*(color|background[-color]*||[a-zA-Z0-9-_]+)??[\s:=]*[\s]*(?:(\b(rgb)\s*?\(\s*?(000|0?\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\s*?,\s*?(000|0?\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\s*?,\s*?(000|0?\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\s*?\))|(\b(rgba)\s*?\(\s*?(000|0?\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\s*?,\s*?(000|0?\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\s*?,\s*?(000|0?\d{1,2}|1\d\d|2[0-4]\d|25[0-5])\s*?,\s*?(0|0\.\d*|1|1.0*)\s*?\))\B|(\b(transparent)|(inherit)|(initial)|(currentColor)|(var)[(]([-]{2}[^)]+)[)])|(#([a-fA-F0-9]){3,4})|(#([a-fA-F0-9]){6,8})|(\b(hsl)\s*?\(\s*?(000|0?\d{1,2}|[1-2]\d\d|3[0-5]\d|360)\s*?,\s*?(000|100|0?\d{2}|0?0?\d)%\s*?,\s*?(000|100|0?\d{2}|0?0?\d)%\s*?\)$)|(\b(hsla)\s*?\(\s*?(000|0?\d{1,2}|[1-2]\d\d|3[0-5]\d|360)\s*?,\s*?(000|100|0?\d{2}|0?0?\d)%\s*?,\s*?(000|100|0?\d{2}|0?0?\d)%\s*?,\s*?(0|0\.\d*|1|1.0*)\s*?\)\b))/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^\\s*(color|background[-color]*||[a-zA-Z0-9-_]+)??[\\s:=]*[\\s]*(?:(\\b(rgb)\\s*?\\(\\s*?(000|0?\\d{1,2}|1\\d\\d|2[0-4]\\d|25[0-5])\\s*?,\\s*?(000|0?\\d{1,2}|1\\d\\d|2[0-4]\\d|25[0-5])\\s*?,\\s*?(000|0?\\d{1,2}|1\\d\\d|2[0-4]\\d|25[0-5])\\s*?\\))|(\\b(rgba)\\s*?\\(\\s*?(000|0?\\d{1,2}|1\\d\\d|2[0-4]\\d|25[0-5])\\s*?,\\s*?(000|0?\\d{1,2}|1\\d\\d|2[0-4]\\d|25[0-5])\\s*?,\\s*?(000|0?\\d{1,2}|1\\d\\d|2[0-4]\\d|25[0-5])\\s*?,\\s*?(0|0\\.\\d*|1|1.0*)\\s*?\\))\\B|(\\b(transparent)|(inherit)|(initial)|(currentColor)|(var)[(]([-]{2}[^)]+)[)])|(#([a-fA-F0-9]){3,4})|(#([a-fA-F0-9]){6,8})|(\\b(hsl)\\s*?\\(\\s*?(000|0?\\d{1,2}|[1-2]\\d\\d|3[0-5]\\d|360)\\s*?,\\s*?(000|100|0?\\d{2}|0?0?\\d)%\\s*?,\\s*?(000|100|0?\\d{2}|0?0?\\d)%\\s*?\\)$)|(\\b(hsla)\\s*?\\(\\s*?(000|0?\\d{1,2}|[1-2]\\d\\d|3[0-5]\\d|360)\\s*?,\\s*?(000|100|0?\\d{2}|0?0?\\d)%\\s*?,\\s*?(000|100|0?\\d{2}|0?0?\\d)%\\s*?,\\s*?(0|0\\.\\d*|1|1.0*)\\s*?\\)\\b))', 'gm') const str = `rgba(0,0,0,0.1); background-color: inherit ; `; // 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