javascript - Why set both env.es6=true and parserOptions.ecmaVersion=6 in .eslintrc.js? - Stack Overflow

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I do not understand why I need to specify the same information in two different parameters,
both env: { es6: true } and parserOptions: { ecmaVersion: 6 }.

module.exports = {
  env: {
    monjs: true,
    es6: true,
    node: true
  },
  extends: [
    'eslint:remended'
  ],
  globals: {
    Atomics: 'readonly',
    SharedArrayBuffer: 'readonly'
  },
  parserOptions: {
    ecmaVersion: 6
  },
};

I do not understand why I need to specify the same information in two different parameters,
both env: { es6: true } and parserOptions: { ecmaVersion: 6 }.

module.exports = {
  env: {
    monjs: true,
    es6: true,
    node: true
  },
  extends: [
    'eslint:remended'
  ],
  globals: {
    Atomics: 'readonly',
    SharedArrayBuffer: 'readonly'
  },
  parserOptions: {
    ecmaVersion: 6
  },
};

• javascript
• node.js
• ecmascript-6
• eslint
• eslintrc

Share Follow edited Nov 1, 2023 at 10:32 Henke - Нава́льный П с м 5,79766 gold badges4141 silver badges5151 bronze badges asked May 22, 2020 at 19:10 MauroMauro 11522 silver badges88 bronze badges 0

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2 Answers 2

Sorted by: Reset to default 6

The ecmaVersion option of parserOptions is for syntax.
The env option is for global variables.

If you want to use a Promise for example, ecmaVersion:latest is not enough.
You also have to specify which environment (env) to use.

Note that the env option automatically enables new syntax.
But personally, I remend setting both of them properly.

From Configure Language Options :

For ES6 syntax, use { "parserOptions": { "ecmaVersion": 6 } }; for new ES6 global variables, use { "env": { "es6": true } }. Setting { "env": { "es6": true } } enables ES6 syntax automatically, but { "parserOptions": { "ecmaVersion": 6 } } does not enable ES6 globals automatically.

For more information, see here.

By this https://eslint/docs/latest/use/configure/language-options#specifying-environments it is enough to set just env which automatically set correct parserOptions.ecmaVersion. So you should prefer this way to avoid mismatch configuration.

es6 - enable all ECMAScript 6 features except for modules (this automatically sets the ecmaVersion parser option to 6).
es2016 - adds all ECMAScript 2016 globals and automatically sets the ecmaVersion parser option to 7.
es2017 - adds all ECMAScript 2017 globals and automatically sets the ecmaVersion parser option to 8.
es2018 - adds all ECMAScript 2018 globals and automatically sets the ecmaVersion parser option to 9.
es2019 - adds all ECMAScript 2019 globals and automatically sets the ecmaVersion parser option to 10.
es2020 - adds all ECMAScript 2020 globals and automatically sets the ecmaVersion parser option to 11.
es2021 - adds all ECMAScript 2021 globals and automatically sets the ecmaVersion parser option to 12.
es2022 - adds all ECMAScript 2022 globals and automatically sets the ecmaVersion parser option to 13.

UPDATE: There must be an error in ESLint doc because I have tested to add env.es2016 : true without parserOptions.ecmaVersion : 2016 and parser is incorrectly fine with async functions which were added later in es2017. So rather set both env and ecmaVersion.

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