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]
  • Character class intersection
    [\w&&[^\d]]
  • 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
Processing...

Test String

Substitution
Processing...

Code Generator

Generated Code

const regex = /^\s*#\s*cancel\s*duplicate.*\n/gmi; // Alternative syntax using RegExp constructor // const regex = new RegExp('^\\s*#\\s*cancel\\s*duplicate.*\\n', 'gmi') const str = `--- # Mega-Linter GitHub Action configuration file # More info at https://megalinter.github.io name: Mega-Linter on: # Trigger mega-linter at every push. Action will also be visible from Pull Requests to main push: # Comment this line to trigger action only on pull-requests (not recommended if you don't pay for GH Actions) pull_request: branches: [master, main] env: # Comment env block if you do not want to apply fixes # Apply linter fixes configuration APPLY_FIXES: all # When active, APPLY_FIXES must also be defined as environment variable (in github/workflows/mega-linter.yml or other CI tool) APPLY_FIXES_EVENT: pull_request # Decide which event triggers application of fixes in a commit or a PR (pull_request, push, all) APPLY_FIXES_MODE: commit # If APPLY_FIXES is used, defines if the fixes are directly committed (commit) or posted in a PR (pull_request) concurrency: group: \${{ github.ref }}-\${{ github.workflow }} cancel-in-progress: true jobs: # Cancel duplicate jobs: https://github.com/fkirc/skip-duplicate-actions#option-3-cancellation-only build: name: Mega-Linter runs-on: ubuntu-latest steps: # Git Checkout - name: Checkout Code uses: actions/checkout@v2 with: token: \${{ secrets.PAT || secrets.GITHUB_TOKEN }} fetch-depth: 0 # Mega-Linter - name: Mega-Linter id: ml # You can override Mega-Linter flavor used to have faster performances # More info at https://megalinter.github.io/flavors/ uses: megalinter/megalinter@v5 env: # All available variables are described in documentation # https://megalinter.github.io/configuration/ VALIDATE_ALL_CODEBASE: \${{ github.event_name == 'push' && github.ref == 'refs/heads/main' }} # Validates all source when push on main, else just the git diff with main. Override with true if you always want to lint all sources GITHUB_TOKEN: \${{ secrets.GITHUB_TOKEN }} # ADD YOUR CUSTOM ENV VARIABLES HERE OR DEFINE THEM IN A FILE .mega-linter.yml AT THE ROOT OF YOUR REPOSITORY # DISABLE: COPYPASTE,SPELL # Uncomment to disable copy-paste and spell checks # Upload Mega-Linter artifacts - name: Archive production artifacts if: \${{ success() }} || \${{ failure() }} uses: actions/upload-artifact@v2 with: name: Mega-Linter reports path: | report mega-linter.log # Create pull request if applicable (for now works only on PR from same repository, not from forks) - name: Create Pull Request with applied fixes id: cpr if: steps.ml.outputs.has_updated_sources == 1 && (env.APPLY_FIXES_EVENT == 'all' || env.APPLY_FIXES_EVENT == github.event_name) && env.APPLY_FIXES_MODE == 'pull_request' && (github.event_name == 'push' || github.event.pull_request.head.repo.full_name == github.repository) uses: peter-evans/create-pull-request@v3 with: token: \${{ secrets.PAT || secrets.GITHUB_TOKEN }} commit-message: "[Mega-Linter] Apply linters automatic fixes" title: "[Mega-Linter] Apply linters automatic fixes" labels: bot - name: Create PR output if: steps.ml.outputs.has_updated_sources == 1 && (env.APPLY_FIXES_EVENT == 'all' || env.APPLY_FIXES_EVENT == github.event_name) && env.APPLY_FIXES_MODE == 'pull_request' && (github.event_name == 'push' || github.event.pull_request.head.repo.full_name == github.repository) run: | echo "Pull Request Number - \${{ steps.cpr.outputs.pull-request-number }}" echo "Pull Request URL - \${{ steps.cpr.outputs.pull-request-url }}" # Push new commit if applicable (for now works only on PR from same repository, not from forks) - name: Prepare commit if: steps.ml.outputs.has_updated_sources == 1 && (env.APPLY_FIXES_EVENT == 'all' || env.APPLY_FIXES_EVENT == github.event_name) && env.APPLY_FIXES_MODE == 'commit' && github.ref != 'refs/heads/main' && (github.event_name == 'push' || github.event.pull_request.head.repo.full_name == github.repository) run: sudo chown -Rc \$UID .git/ - name: Commit and push applied linter fixes if: steps.ml.outputs.has_updated_sources == 1 && (env.APPLY_FIXES_EVENT == 'all' || env.APPLY_FIXES_EVENT == github.event_name) && env.APPLY_FIXES_MODE == 'commit' && github.ref != 'refs/heads/main' && (github.event_name == 'push' || github.event.pull_request.head.repo.full_name == github.repository) uses: stefanzweifel/git-auto-commit-action@v4 with: branch: \${{ github.event.pull_request.head.ref || github.head_ref || github.ref }} commit_message: "[Mega-Linter] Apply linters fixes" `; const subst = ``; // The substituted value will be contained in the result variable const result = str.replace(regex, subst); console.log('Substitution result: ', result);

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