ESLint 0.12.0 released

by Nicholas C. Zakas - 17 January 2015

We just pushed ESLint 0.12.0, which is a minor release upgrade. This release includes new features and bug fixes.


This is a summary of the major changes you need to know about for this version of ESLint.

Partial ECMAScript 6 support

0.12.0 introduces support for several ECMAScript 6 features, including:

  • let and const
  • Regular expression y flag
  • Regular expression u flag
  • Binary literals
  • Octal literals
  • for-of
  • Generators
  • Object literal syntax changes

All of these options are off by default, and you can enable them in your configuration file. See Configuring ESLint for more information.

We also have two rules that are specific for ES6: no-var and generator-star.

Known limitation: Block scope calculation doesn't work yet for let and const. We are actively working on fixing that. This may affect rules like no-unused-vars until we resolve this (hopefully soon).

JSX support

0.12.0 also has full support for the JSX extension created by Facebook. ESLint now fully supports JSX natively (it's not transformed before linting). JSX parsing is off by default, and you can enable it in your configuration file. This is being tracked in #917.

es6jsx end-of-life

The es6jsx branch is now considered obsolete and changes will continue to be merged into the master branch. Please make sure you're using the latest stable ESLint going forward.

Breaking Changes

  • Breaking: Allow parser feature flips (fixes #1602) (Nicholas C. Zakas)


  • New: gen-star rule (refs #1617) (Jamund Ferguson)
  • New: no-var rule (refs #1617) (Jamund Ferguson)

Bug Fixes

  • Fix: Allow comments in key-spacing groups (fixes #1632) (Brandon Mills)
  • Fix: Allow individual newlines in space-in-brackets (fixes #1614) (Brandon Mills)
  • Fix: block-scoped-var reports labels (fixes #1630) (Michael Ficarra)
  • Fix: Broken JSX test (Nicholas C. Zakas)
  • Fix: Don't warn on JSX literals with newlines (fixes #1533) (Nicholas C. Zakas)
  • Fix: Find JSXIdentifier refs in no-unused-vars (fixes #1534) (Nicholas C. Zakas)
  • Fix: no-bitwise reports on bitwise assignment expressions (fixes #1643) (Mathias Schreck)
  • Fix: Property regex flag checking (fixes #1537) (Nicholas C. Zakas)
  • Fix: quotes rule ignores JSX literals (fixes #1477) (Nicholas C. Zakas)
  • Fix: Support JSX spread operator (fixes #1634) (Nicholas C. Zakas)
  • Fix: Track JSX global variable correctly (fixes #1534) (Nicholas C. Zakas)


  • Update: Update optionator, --no in help (fixes #1134) (George Zahariev)
  • Update: Add a couple JSX tests (Nicholas C. Zakas)
  • Update: Expose ecmaFeatures on context (fixes #1648) (Nicholas C. Zakas)
  • Update: Fully enable JSX support (fixes #1640) (Nicholas C. Zakas)

Dependency Upgrades

  • Upgrade: several dependencies (fixes #1377) (Nicholas C. Zakas)


  • Docs: Add angularjs-eslint link into the integration doc (Emmanuel DEMEY)
  • Docs: add newline to no-process-env (fixes #1627) (Tom Vincent)
  • Docs: Added Fitbit to the list of companies (Igor Zalutsky)
  • Docs: Correct alignment in example project tree (Tim Schaub)
  • Docs: Document ecmaFeatures (Nicholas C. Zakas)
  • Docs: Remove illegal code fence (Nicholas C. Zakas)
  • Docs: Remove references to Esprima (Nicholas C. Zakas)