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

/
/
mx

Test String

Code Generator

Language

Generated Code

const regex = /(?:\s*from\s(?:(?:([^\(\n]*?)\s)|(\[[^\]]*\]))?(?:\((?:(?:((?!HELO|EHLO)[^\s]*)|(?:(?:EHLO)|(?:HELO)))?(?:[\s\w\.]*(?:(?:\[([^\]]*)\])|([^\)\s]*))\))))?(?:\{.*\})?)? \s*(?:(?:client\s)?[\(\{\[]+([^\)\}\]]*)[\)\}\]]+\;?(?:\{.*\})?)? (?:[\s\n]*) (?:\s*(?:by(?:(?:.*?)(?:\;|(?:[\r\n]+))))(?!.*with))? (?:\s*(?:by\s[^\;]*\)?)(?=.*with)\s*)? (?:with\s*(?:((?:[^\n;]*))(?:.*\;)?))? (?:[\s\n]*)? (?:\(?envelope-from\s*([^\n]*)\;?\)?)? (?:\s*id[^;]*\;?)? (?:[\s\n]*)? (?:for\s([^\;]*)\;)? (?:[\s\n]*)? (?:\(.*\)\;)?(?:[\s\n])? ([^\(]+)? (?:\(?envelope-from\s*([^\n]*)\;?\)?)?/m; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?:\\s*from\\s(?:(?:([^\\(\\n]*?)\\s)|(\\[[^\\]]*\\]))?(?:\\((?:(?:((?!HELO|EHLO)[^\\s]*)|(?:(?:EHLO)|(?:HELO)))?(?:[\\s\\w\\.]*(?:(?:\\[([^\\]]*)\\])|([^\\)\\s]*))\\))))?(?:\\{.*\\})?)? \\s*(?:(?:client\\s)?[\\(\\{\\[]+([^\\)\\}\\]]*)[\\)\\}\\]]+\\;?(?:\\{.*\\})?)? (?:[\\s\\n]*) (?:\\s*(?:by(?:(?:.*?)(?:\\;|(?:[\\r\\n]+))))(?!.*with))? (?:\\s*(?:by\\s[^\\;]*\\)?)(?=.*with)\\s*)? (?:with\\s*(?:((?:[^\\n;]*))(?:.*\\;)?))? (?:[\\s\\n]*)? (?:\\(?envelope-from\\s*([^\\n]*)\\;?\\)?)? (?:\\s*id[^;]*\\;?)? (?:[\\s\\n]*)? (?:for\\s([^\\;]*)\\;)? (?:[\\s\\n]*)? (?:\\(.*\\)\\;)?(?:[\\s\\n])? ([^\\(]+)? (?:\\(?envelope-from\\s*([^\\n]*)\\;?\\)?)?', 'm') const str = `from qzienfhr ([182.109.196.197]) by mail.oucu.edu.eg with SMTP (Code-Crafters Ability Mail Server 2012); Mon, 03 Dec 2018 12:42:56 +0200`; // Reset `lastIndex` if this regex is defined globally // regex.lastIndex = 0; 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