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

/
/
gu

Test String

Code Generator

Generated Code

import java.util.regex.Matcher; import java.util.regex.Pattern; public class Example { public static void main(String[] args) { final String regex = "(?<=^|[\\n;](?:[\\t ]*(?:\\w+ )?)?)(?:(?:const\\s*|let\\s*|var\\s*)?(?<imports>(?:[$_\\p{ID_Start}][$\\u200C\\u200D\\p{ID_Continue}]*)|(?<=const\\s*|let\\s*|var\\s*)(?:[\\w\\t\\n\\r \"$'*,./:\\{\\}-]+?))\\s*=\\s*)?(?:await\\s+)?(?<expression>import\\((?<specifier>[\\S\\t\\n\\r]+?)(?:,\\s*(?<options>\\{\\s*assert:.+[\\w\\t\\n\\r \"':]+\\}\\s*\\}))?\\))"; final String string = "await import(foo)\n" + "await import('foo')\n" + "const foo = await import('bar')\n" + "const foo = await import(bar)\n" + "const promise = import('./foo');\n" + "const { readPackage } = await import('read-pkg')\n" + "const { \n" + " readPackageUp,\n" + " readPackageUpSync\n" + "} = await import('read-pkg');\n" + "const {\n" + " addFive,\n" + " addFour,\n" + " addThree,\n" + " addTwo,\n" + " squareFive,\n" + " squareFour,\n" + " squareThree,\n" + " squareTwo\n" + "} = await import('./lib')\n" + "await import('buzz').then(() => console.log(res)).catch(() => ({}))\n" + "var g;const{foo}=await import('bar');const{ foo }=await import('bar')\n" + "import('buzz').then(() => console.log(res)).catch(() => ({}))\n" + "import('buzz').then(() => console.log(res)).catch(() => ({}))\n\n" + "import('buzz').catch(() => ({}))\n\n" + "const foo = \"./utils.mjs\"; await import(foo)\n\n" + "const { default: barData } =\n" + " await import('./bar.json');\n\n" + "const { default: barData } =\n" + " await import('./bar.json', { assert: { type: 'json' } });\n\n" + "(async () => {\n" + " if (somethingIsTrue) {\n" + " // import module for side effects\n" + " await import(\"/modules/my-module.js\");\n" + " }\n" + "})();\n\n" + "await import('__tests__/report.json', { \n" + " assert: { type: 'json' }\n" + "})\n\n" + " await import('__tests__/report.json', {\n" + " assert: { type: 'json' }\n" + " })\n\n" + "(async () => {\n" + " if (somethingIsTrue) {\n" + " const {\n" + " default: myDefault,\n" + " foo,\n" + " bar,\n" + " } = await import(\"/modules/my-module.js\");\n" + " }\n" + "})();\n\n" + "const main = document.querySelector(\"main\");\n" + "for (const link of document.querySelectorAll(\"nav > a\")) {\n" + " link.addEventListener(\"click\", (e) => {\n" + " e.preventDefault();\n\n" + " import(\"/modules/my-module.js\")\n" + " .then((module) => {\n" + " module.loadPageInto(main);\n" + " })\n" + " .then((module) => {\n" + " module.loadPageInto(main);\n" + " })\n" + " .then((module) => {\n" + " module.loadPageInto(main);\n" + " })\n" + " .catch((err) => {\n" + " main.textContent = err.message;\n" + " });\n" + " });\n" + "}\n\n" + "let myModule;\n\n" + "if (typeof window === \"undefined\") {\n" + " myModule = await import(\"module-used-on-server\");\n" + "} else {\n" + " myModule = await import(\"module-used-in-browser\");\n" + "}\n\n" + "Promise.all(\n" + " Array.from({ length: 10 }).map((_, index) =>\n" + " import(`/modules/module-${index}.js`)\n" + " )\n" + ").then((modules) => modules.forEach((module) => module.load()));\n\n" + " Array.from({ length: 10 }).map((_, index) => {\n" + " return import(`/modules/module-${index}.js`)\n" + " })\n\n" + "'await import(\"foo\")'\n" + "\"await import('foo')\"\n\n" + "// await import('foo')\n\n" + "/**\n" + " * @example\n" + " * const { readPackageUp } = await import('read-pkg')\n" + " */\n"; final Pattern pattern = Pattern.compile(regex, Pattern.UNICODE_CASE); final Matcher matcher = pattern.matcher(string); while (matcher.find()) { System.out.println("Full match: " + matcher.group(0)); for (int i = 1; i <= matcher.groupCount(); i++) { System.out.println("Group " + i + ": " + matcher.group(i)); } } } }

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 Java, please visit: https://docs.oracle.com/javase/7/docs/api/java/util/regex/Pattern.html