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eslint creating error `Parsing error: Parenthesized pattern`

See original GitHub issue

Tell us about your environment Mac OS

  • ESLint Version: “eslint”: “^3.16.1”,

  • Node Version: node v6.10.2

  • npm Version: npm v3.10.10

What parser (default, Babel-ESLint, etc.) are you using? default Please show your full configuration:

    "env": {
        "browser": true,
        "commonjs": true,
        "node": true
    "globals": {
        "Uint8Array": false,
        "describe": false,
        "before": false,
        "it": false
    "extends": "eslint:recommended",
    "rules": {
        "no-console": [
            {"allow": ["warn"]}
        "linebreak-style": [
        "semi": [

What did you do? Please include the actual source code causing the issue, as well as the command that you used to run ESLint.

var groupBy = function(array, cp){
    return array.reduce((groups, next) => { const name = cp(next);
    if (name !== undefined) {
        const group = groups.get(name);
        if (group) group.push(next);
        else groups.set(name, [next]);
    return groups;
}, new Map());

npm run lint

What did you expect to happen? no lint error for return array.reduce((groups, next) => { const name = cp(next); What actually happened? Please include the actual, raw output from ESLint. gave following error:

  19:25  error  Parsing error: Parenthesized pattern

✖ 1 problem (1 error, 0 warnings)

npm ERR! Darwin 15.6.0
npm ERR! argv "/usr/local/bin/node" "/usr/local/bin/npm" "run" "lint"
npm ERR! node v6.10.2
npm ERR! npm  v3.10.10
npm ERR! bids-validator@0.0.0 lint: `./node_modules/eslint/bin/eslint.js ./**/*.js`
npm ERR! Exit status 1
npm ERR!
npm ERR! Failed at the bids-validator@0.0.0 lint script './node_modules/eslint/bin/eslint.js ./**/*.js'.
npm ERR! Make sure you have the latest version of node.js and npm installed.
npm ERR! If you do, this is most likely a problem with the bids-validator package,
npm ERR! not with npm itself.
npm ERR! Tell the author that this fails on your system:
npm ERR!     ./node_modules/eslint/bin/eslint.js ./**/*.js
npm ERR! You can get information on how to open an issue for this project with:
npm ERR!     npm bugs bids-validator
npm ERR! Or if that isn't available, you can get their info via:
npm ERR!     npm owner ls bids-validator
npm ERR! There is likely additional logging output above.

Issue Analytics

  • State:closed
  • Created 6 years ago
  • Comments:10 (6 by maintainers)

github_iconTop GitHub Comments

platinumazurecommented, Dec 10, 2017

I don’t see you using ES6 in your configuration. Without ES6, you can’t use arrow functions.

Try adding this to your config: "parserOptions": { "ecmaVersion": 6 }

not-an-aardvarkcommented, Jan 19, 2018

Closing because there hasn’t been a response in awhile – feel free to create a new issue if you’re still having trouble.

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