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 = /^(?<protocol>jsr:|npm:|node:)(\/*(@(?<scope>[^\/\s]+)\/)?(?<pkg>[^@\/\s]+)(@(?<version>[^\/\r\n\t\f\v]+))?)?(?<pathname>\/.*)?$/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('^(?<protocol>jsr:|npm:|node:)(\\\/*(@(?<scope>[^\\\/\\s]+)\\\/)?(?<pkg>[^@\\\/\\s]+)(@(?<version>[^\\\/\\r\\n\\t\\f\\v]+))?)?(?<pathname>\\\/.*)?$', 'gm') const str = `npm:/@scope/package@version/pathname npm:package@version/pathname npm:package npm:package/pathname npm:package@version npm:package@version/pathname npm:/package npm:/package/pathname npm:/package@version npm:/package@version/pathname npm:@scope/package npm:@scope/package/pathname npm:@scope/package@version npm:@scope/package@version/pathname npm:/@scope/package npm:/@scope/package/pathname npm:/@scope/package@version npm:/@scope/package@version/pathname npm://////package/pathname jsr:package jsr:package/pathname jsr:package@version jsr:package@version/pathname jsr:/package jsr:/package/pathname jsr:/package@version jsr:/package@version/pathname jsr:@scope/package jsr:@scope/package/pathname jsr:@scope/package@version jsr:@scope/package@version/pathname jsr:/@scope/package jsr:/@scope/package/pathname jsr:/@scope/package@version jsr:/@scope/package@version/pathname jsr://////package/pathname jsr:@scope/package@~2.2.0/pathname/file.ts jsr:@scope/package@>2.1/pathname/dirname/ jsr:@scope/package@1.0.0 - 1.2.0/pathname/file.ts jsr:package@^2 <2.2 || > 2.3 jsr:@scope/package@>=1.0.0-rc.0 <1.0.1 `; // 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