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 = /Received\s*:\s*by.*?(?P<Hop_Time>[0-9]{2}:[0-9]{2}:[0-9]{2})/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('Received\\s*:\\s*by.*?(?P<Hop_Time>[0-9]{2}:[0-9]{2}:[0-9]{2})', 'gm') const str = `Received:by mail-ed1-f69.google.com with SMTP id b21so4825939edt.18 for <budsarin.temsawat@aaa.co.th>; Wed 26 Jun 2019 18:04:32 -0700 (PDT) X-Google-DKIM-Signature:v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:references:in-reply-to:from:date :message-id:subject:to:cc; bh=q04dTGosad+dTkX0DLE3TZT1LvNQX45YXfBh9AMeFco=; b=a5lzAB+U25QwdRDIw/0H1CT0SGRZNRyiTRNJ1jg5kgfg4IPhyOeWkqm72Ay w1VV8x3kVzv2jgAyF9/W57NcN43CyejW+ag086fJy2LmqMM03q/Voz7A89av nxsiIx0V5BOWkcSl3XdBOqQD9imxNL9Bermp548jum51kOopBX6uALrW+Yy qfSravlh8ONQ8YTOC47iSPBQhCh0b1lMO51p5e6zeIwcLUO62YYl/N3DUKDeN vduYOj/HAEVQXqfO64Fepx6U2QAi2Lg6hM2zcdKMgDR/Wdj/QehmFj+Fl Ptag== X-Gm-Message-State:APjAAAUcvfjYPCkT4REkr2t4IE6NeIZTGRWloRcKwy0gyZHb MynBUQciUYH9gQifGU0TaLv4ddVqHoFhsAXIsniMfUuXeetryhOwO+1bS26ze2SA fvZIq6qEaOgJlMJZt9nUOMYE2WspxuBWVosL2kKutE99i5q9VzsMDuK+2wlVL4y MZOpqMIpA6mfKRnzX1cwrcvA9PPbiWI/x7Ldg0kx+kCRuuJQ== X-Received:by 2002:a17:906:3ed1:: with SMTP id d17mr602603ejj.285.1561597403255; Wed 26 Jun 2019 18:03:23 -0700 (PDT) X-Google-Smtp-Source:APXvYqw4u4lwcGK+asj4XNave7dmVhuneOG1zr46FOmbsgkj0gup9KvdYrzB1LJXS2zMNXf+I= X-Received:by 2002:a17:906:3ed1:: with SMTP id d17mr602584ejj.285.1561597403013; Wed 26 Jun 2019 18:03:23 -0700 (PDT) MIME-Version:1.0 References:<CAB-UEWaNHyJz4EyotLZA@mail.gmail.com> <CAB-UEWavdVz0J+ySP5u_GGZm+DVRg@mail.gmail.com> <CANAFqSiHpjuU5VNQ57MSwc9FuGfwMEu49EvSQ@mail.gmail.com> <CAB-UEWZBhEzT2QxwsBk-XBfzf7j0qHr5O7tyUxwQw@mail.gmail.com> <CANAFqSiKEMRGkFsA2awnVg5zKSmih6iGOAv7Ng@mail.gmail.com> In-Reply-To:<CANAFqSiKEMRGkFsA2=4wnVg5zKSmih6iGOAv7Ng@mail.gmail.com> From:Sirisri Jitvatkun <sirisri.jitvatkun@bbb.co.th> Date:Thu 27 Jun 2019 08:03:11 +0700 `; // 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