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

const regex = /(?<=^|[\n;](?:[\t ]*(?:\w+ )?)?)export\s*(?<modifiers>(?:\s*declare|\s*abstract|\s*async)+)?\s*(?<declaration>class|const +enum|const|enum|function\*?|interface|let|namespace|type(?! *\{)|var)\s+(?<exports>(?:[$_\p{ID_Start}][$\u200C\u200D\p{ID_Continue}]*(?=[\s=:;/({])(?!.*?,))|(?:[\w\t\n\r .,:$'"=-]+)|(?:[{[][\w\t\n\r .,:$'"-]+[}\]]))(?:\s*=\s*[$_\p{ID_Start}][$\u200C\u200D\p{ID_Continue}]*)?/gu; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?<=^|[\\n;](?:[\\t ]*(?:\\w+ )?)?)export\\s*(?<modifiers>(?:\\s*declare|\\s*abstract|\\s*async)+)?\\s*(?<declaration>class|const +enum|const|enum|function\\*?|interface|let|namespace|type(?! *\\{)|var)\\s+(?<exports>(?:[$_\\p{ID_Start}][$\\u200C\\u200D\\p{ID_Continue}]*(?=[\\s=:;\/({])(?!.*?,))|(?:[\\w\\t\\n\\r .,:$\'"=-]+)|(?:[{[][\\w\\t\\n\\r .,:$\'"-]+[}\\]]))(?:\\s*=\\s*[$_\\p{ID_Start}][$\\u200C\\u200D\\p{ID_Continue}]*)?', 'gu') const str = `export const CJS_SYNTAX_REGEX: RegExp = /pattern/gm;export const IGNORE_PATTERNS: string[] = []; export declare const RESOLVE_EXTENSIONS: string[] export enum Snack{} export const enum Snack {} export interface User {} export class House {} export declare abstract class House extends Building {} export abstract class House {} export async function run() {} export async function* run() {} export function foo() {} export function* foo() {} export const \$foo = 42 export const \$foo= 42 export namespace Foo {} export type Foo = 'foo' export let name1, name2/*, … */; // also var export const name1 = 1, name2 = 2/*, … */; // also var, let export function functionName() { /* … */ } export class ClassName { /* … */ } export function* generatorFunctionName() { /* … */ } export const { name1, name2: bar } = o; export const [ name1, name2 ] = array; declare module 'module-name' { export declare abstract class Building {} export declare class House extends Building {} } "export const \$foo = 42" export default async function functionName() { /* … */ } export default function functionName() { /* … */ } export default function* generatorName() { /* … */ } export default async function* generatorNameAsync() { /* … */ } export default class ClassName { /* … */ } export default abstract class ClassName { /* … */ } export default function () { /* … */ } export default async function () { /* … */ } export default function* () { /* … */ } export default async function* () { /* … */ } export default class { /* … */ } export default async () => {} export default async arg => {} export default () => {} export default arg => {} export default (arg) => {} export default foo export default foo; export default 1 + 1; // export const CJS_SYNTAX_REGEX /** * Resolvable file extensions. * * @example * export const CJS_SYNTAX_REGEX */ export type Foo = 'foo'`; // 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