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

/
/
g

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+ )?)?)import\\s*(?<type>type(?=\\s+))?(?:[\\s\"']*(?<imports>[\\w\\t\\n\\r \"$'*,/\\{\\}-]+?)\\s+from\\s*)?[\"']\\s*(?<specifier>(?:(?<='\\s*)[^']*[^\\s'](?=\\s*'))|(?:(?<=\"\\s*)[^\"]*[^\\s\"](?=\\s*\")))\\s*[\"'](?:\\s+assert\\s+(?<assertion>\\{[\\w\\t\\n\\r \"':]+?\\}))?(?=[\\s;]*)"; final String string = "/**\n" + " * @file Interfaces\n" + " * @module mlly/interfaces\n" + " */\n\n" + "export type { default as DynamicImport } from './import-dynamic'\n" + "export type { default as StaticImport } from './import-static'\n" + "export type { default as ResolveOptions } from './options-resolve'\n" + "export type { default as ResolveAliasOptions } from './options-resolve-alias'\n" + "export type { default as Statement } from './statement'\n" + "export type { default as ExportStatement } from './statement-export'\n" + "export type { default as ImportStatement } from './statement-import'\n" + "export type { default as RequireStatement } from './statement-require'\n\n" + "import { CONDITIONS, RESOLVE_EXTENSIONS } from '#src/constants'\n" + "import type { ResolveOptions } from '#src/interfaces'\n" + "import type { SpecifierType } from '#src/types'\n" + "import isBuiltin from '@flex-development/is-builtin'\n" + "import { moduleResolve, type ErrnoException } from 'import-meta-resolve'\n" + "import { pathToFileURL, URL } from 'node:url'\n" + "import upath from 'upath'\n" + "import toBareSpecifier from './to-bare-specifier'\n" + "import toRelativeSpecifier from './to-relative-specifier'\n" + "import 'file:///home/dir/file.ts'\n\n" + "import pkg from './package.json' assert { type:'json' }\n" + "import * as color from 'colorette'\n" + "import consola from 'consola'\n" + "import { defu } from 'defu'\n" + "import type { Format } from 'esbuild'\n" + "import fse from 'fs-extra'\n" + "import * as pathe from 'pathe'\n" + "import { resolve } from 'node:path'\n" + "import url from 'node:url'\n" + "import type { PackageJson } from 'pkg-types'\n" + "import pb from 'pretty-bytes'\n" + "import { EXT_DTS_REGEX, IGNORE_PATTERNS } from './config/constants'\n" + "import loadBuildConfig from './config/load'\n" + "import type { Config, Entry, Result } from './interfaces'\n" + "import type { OutputExtension } from './types'\n" + "import { readPackage, type PackageJson } from \"read-pkg\"\n" + "import {OutputExtension} from './types'\n" + "import analyzeResults from './utils/analyze-results'\n" + "import esbuilder from './utils/esbuilder'; import write from './utils/write';import write2 from './utils/write'\n" + "// import write from './utils/write'\n" + "import 'side-effect.mjs'\n" + "import type StatementType from '../types/statement-type'\n" + "import type {\n" + " BuildOptions,\n" + " BuildResult,\n" + " OutputFile,\n" + " Plugin,\n" + " PluginBuild\n" + "} from './esbuild'\n\n" + "import defaultExport from \"module-name\";\n" + "import * as name from \"module-name\";\n" + "import { export1 } from \"module-name\";\n" + "import { export1 as alias1 } from \"module-name\";\n" + "import { default as alias } from \"module-name\";\n" + "import { export1, export2 } from \"module-name\";\n" + "import { export1, export2 as alias2 } from \"module-name\";\n" + "import { 'string name' as alias } from \"module-name\";\n" + "import { \"string name\" as alias } from \"module-name\";\n" + "import defaultExport, { export1 } from \"module-name\";\n" + "import defaultExport, * as name from \"module-name\";\n" + "import \"module-name\";\n" + "import 'module-name';\n" + "import './polyfill.mjs'\n" + "import { \"h-i\" as hi } from './hi.js'\n" + "import { 'j-k' as jk } from \"./jk.js\"\n\n" + "declare module '__fixtures__/values' {\n" + " import MAX_VALUE from '#fixtures/max-value'\n" + " import MIN_VALUE from '#fixtures/min-value'\n" + "}\n\n" + "const ERR_UNSUPPORTED_DIR_IMPORT: NodeErrorConstructor<\n" + " ErrorConstructor,\n" + " [string, string]\n" + "> = createNodeError(\n" + " ErrorCode.ERR_UNSUPPORTED_DIR_IMPORT,\n" + " Error,\n" + " 'Directory import '%s' is not supported resolving ES modules imported from %s'\n" + ")\n\n" + "const text: string = await resolveModules(output.text, {\n" + " conditions: [format === 'esm' ? 'import' : 'require'],\n" + " ext: ext as Ext,\n" + " extensions,\n" + " parent\n" + "})\n\n" + "/**\n" + " * @example\n" + " * import write from './utils/write'\n" + " * write()\n" + " */\n\n" + "import { 'j-k' as jk } from \"./jk.js\""; final Pattern pattern = Pattern.compile(regex); 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