Regular Expressions 101

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  • Unit Tests (17)

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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
  • Match everything enclosed
    (?:...)
  • Capture everything enclosed
    (...)
  • 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

Generated Code

const regex = /(?:(?<=(?:import|export)[^`'"]*from\s+[`'"])(?<path1>[^`'"]+)(?=(?:'|"|`)))|(?:\b(?:import|export)(?:\s+|\s*\(\s*)[`'"](?<path2>[^`'"]+)[`'"])/gm; // Alternative syntax using RegExp constructor // const regex = new RegExp('(?:(?<=(?:import|export)[^`\'"]*from\\s+[`\'"])(?<path1>[^`\'"]+)(?=(?:\'|"|`)))|(?:\\b(?:import|export)(?:\\s+|\\s*\\(\\s*)[`\'"](?<path2>[^`\'"]+)[`\'"])', 'gm') const str = `import { defaultTemplateProcessor } from './lib/default-template-processor.js'; import { SVGTemplateResult, TemplateResult } from './lib/template-result.js'; export { DefaultTemplateProcessor, defaultTemplateProcessor } from './lib/default-template-processor.js'; export { directive, isDirective } from './lib/directive.js'; export { removeNodes, reparentNodes } from './lib/dom.js'; export { noChange, nothing } from './lib/part.js'; export { AttributeCommitter, AttributePart, BooleanAttributePart, EventPart, isIterable, isPrimitive, NodePart, PropertyCommitter, PropertyPart } from './lib/parts.js'; export { parts, render } from './lib/render.js'; export { templateCaches, templateFactory } from './lib/template-factory.js'; export { TemplateInstance } from './lib/template-instance.js'; export { SVGTemplateResult, TemplateResult } from './lib/template-result.js'; export { createMarker, isTemplatePartActive, Template } from './lib/template.js'; import { render } from 'lit-html/lib/shady-render.js'; import { UpdatingElement } from './lib/updating-element.js'; export * from './lib/updating-element.js'; export * from './lib/decorators.js'; export { html, svg, TemplateResult, SVGTemplateResult } from 'lit-html/lit-html.js'; import { supportsAdoptingStyleSheets } from './lib/css-tag.js'; export * from './lib/css-tag.js'; import { LitElement } from 'lit-element'; import { IronMeta } from '@polymer/iron-meta/iron-meta.js'; import { whenOnline } from 'hadron-core/lib/utils/async.js'; import { apiUrl, apiVersion } from '../../src/config.js'; import { importModule, dynamicImportAvailable } from '../../src/dynamic-imports-polyfill.js'; import observeProperties from 'hadron-core/lib/utils/object-property-observer.js'; export { version }; import { ElementMixin, version } from './lib/mixins/element-mixin.js'; export { html } from './lib/utils/html-tag.js'; class Foo { constructor() { import(\`foo.js\`); import(\`\${foo}\`); import('bar.js'); } }`; // 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