Welcome to ReactEsLint


We want to lint our code to see if it meets some basic requirements. The most important part is setting up ESLint at the command line, but we also want it working WebStorm.


This 15 minute video covers some of the same material discussed in this assignment. Most of what you need to know is in the first 5 to 8 minutes of the video:

Install Globally

I now think there is value in installing these globally, and not just on a per-project basis. If you want to install it globally, try these commands:

npm i -g eslint
npm i -g eslint-plugin-react
npm i -g eslint-plugin-requirejs
npm i -g babel-eslint

Read here for more details.

Alternative Local Installation

Alternatively, you can install these packages locally:

npm install --save-dev eslint
npm install --save-dev eslint-plugin-react
npm install --save-dev babel-eslint


npm install --save-dev eslint eslint-plugin-react babel-eslint

If you do this, then you need to type something like this to reach eslint or prettier:

./node_modules/.bin/eslint .

It's probably simpler to install them globally, but there are good reasons for each approach.

Getting Yarn's Global Bin Directory on your PATH

On Pristine Lubuntu, I long ago made sure that ~/npm/bin is on the path. Therefore globally installed NPM packages are available to everyone. I have not, however, yet set up yarn's global directory to be on the path.

So I guess what we want on the path is the directory I list here:

$ ll  
total 0  
drwxrwxrwx 1 charlie charlie 512 May 10 11:11 ./  
drwxrwxrwx 1 charlie charlie 512 May 10 11:11 ../  
lrwxrwxrwx 1 charlie charlie 18 May 10 11:11 bower -> ../bower/bin/bower*  
lrwxrwxrwx 1 charlie charlie 28 May 10 11:11 create-react-app -> ../create-react-app/index.js*  
lrwxrwxrwx 1 charlie charlie 37 May 10 11:11 css-beautify -> ../js-beautify/js/bin/css-beautify.js*  
lrwxrwxrwx 1 charlie charlie 39 May 10 11:11 express -> ../express-generator/bin/express-cli.js*  
lrwxrwxrwx 1 charlie charlie 38 May 10 11:11 html-beautify -> ../js-beautify/js/bin/html-beautify.js*  
lrwxrwxrwx 1 charlie charlie 36 May 10 11:11 js-beautify -> ../js-beautify/js/bin/js-beautify.js*  
lrwxrwxrwx 1 charlie charlie 25 May 10 11:11 nodemon -> ../nodemon/bin/nodemon.js*  
lrwxrwxrwx 1 charlie charlie 21 May 10 11:11 npm -> ../npm/bin/npm-cli.js*  
lrwxrwxrwx 1 charlie charlie 21 May 10 11:11 npx -> ../npm/bin/npx-cli.js*

We should, therefore, add this near the bottom of our ~/.bashrc:

#Yarn Support

set-system-path "$HOME/.config/yarn/global/node_modules/.bin"

Here is set-system-path, which should already be in your .bashrc:

set-system-path () {  
  if ! echo "$PATH" | /bin/grep -Eq "(^|:)$1($|:)" ; then  
    export PATH="$1:$PATH"  

That seems to be working for me, so I've added it in JsObject for future generations.

NOTE: You might be in one of those generations, so perhaps this has already been done for you.

Check whether your apps are installed for Yarn (.config/yarn/global/node_modules/) or npm (~/npm/node_modules)?

Which is on your path? If you type which eslint what comes up? Here is how it looks for me:

$ which eslint

That means I'm running the NPM install of eslint, not the yarn install of eslint. Therefore, something like babel-eslint should be installed in with npm. Alternatively, uninstall the npm version of eslint.

RC File

And here is at least a starter .eslintrc file:

To get the gist, or other related files discussed in this assignment, try running my script called get-gist.

Arrow Functions

I'm not clear about this. Set "parser": "babel-eslint" in .eslintrc to allow arrow functions.

Run from command line

Assuming your ES6 code is in project tree, do one of these, where the first is for the global install, and the second is for the local install:

$ eslint .


$ ./node_modules/.bin/eslint .

Also, consider putting it in your package.json file in the scripts section. For instance you might write something like this in one of your package.json files:

"scripts": {
    "start": "DEBUG=firebase-express:server nodemon ./bin/www",
    "bundle": "node_modules/.bin/webpack --watch",
    "lint": "./node_modules/.bin/eslint ."

When I ran npm run lint, it worked, but NPM reports an error until I get all the eslint errors and warnings out of my code. Then it returns cleanly. Before that, I see the results of my tests, but NPM reports an error

Add .eslintignore

Add a file called .eslintignore so that eslint does not try to parse files that we did not create. For instance, your file might have this content:



Often you can automatically fix errors in your code like this:

eslint --fix .

For instance, I run eslint and get multiple errors, then I run eslint . --fix and it afterwards eslint comes back clean:

charlie@rohan-mintc ~/Git/isit322-calvert-2018/GitExplorer (Week06-Charlie)
$ eslint .

  11:1  error  Expected indentation of 4 spaces but found 0  indent

  39:17  warning  Strings must use singlequote  quotes
  39:65  warning  Strings must use singlequote  quotes
  49:17  warning  Strings must use singlequote  quotes
  51:21  warning  Strings must use singlequote  quotes

✖ 5 problems (1 error, 4 warnings)
  1 error, 4 warnings potentially fixable with the `--fix` option.

charlie@rohan-mintc ~/Git/isit322-calvert-2018/GitExplorer (Week06-Charlie)
$ eslint . --fix
charlie@rohan-mintc ~/Git/isit322-calvert-2018/GitExplorer (Week06-Charlie)
$ eslint .
charlie@rohan-mintc ~/Git/isit322-calvert-2018/GitExplorer (Week06-Charlie)

Case Statements

I was having trouble with case statements and recently updated the [gist] file eslintrc.json to include this code:

"indent": ["error", 4, {"SwitchCase": 1}],

The little SwitchCase object literal seems to have solved the problem. I hope.


In WebStorm, turn on ESLint.

File | Settings | Languages and Frameworks | JavaScript | Code Quality Tools

My current thinking is that we should use EsLint, and EsLint only, to lint our React programs. You can, therefore, turn off JsHint and JSCS. You only need to be running ESLint.

Turn it in

Just point me at your midterm, final, or current project. When I open it, I'll expect to see a .eslintrc.json file and have most of the files relatively error free in terms of eslint errors.


For help formatting files, I'm moving from js-beautify to prettier. The first time we use it, we need to be sure it is installed. Once we have installed it, it stays installed. So we need to run one of these commands only once:

npm install --global prettier

Install with yarn:

yarn global add prettier

NOTE: When installing npm packages globally, use NPM rather than yarn. If you really want yarn, make sure the place that yarn puts them is on your path. I've already set things up on Pristine Lubuntu so that npm global packages are on your path. See the bottom of ~/.bashrc for details.

You can set up a configuration file called .prettierrc in the root of your project or repository:

    "tabWidth": 4,
    "singleQuote": true

We run prettier to clean up the format of our files before we turn in an assignment. We don't want to run it on all files in our project. For instance, we don't want to format the files in node_modules since we don't own them.

To ensure we operate on only the files we want to format, create a script called prettier like this:


find . -iname "*.js" \
  -not -path "**/node_modules/**" \
  -not -path "**/bower_components/**" \
  -not -path "**/bundle.js" \
  -not -path "**/registerServiceWorker.js" \
  -exec "prettier" --write {} \;

Make it executable:

chmod +x prettier

Call it like this:


If you want more, see also FindNpPrettier in JsObjects. You can install that script with these commands:


See the CreateSymbolicLinks script on GitHub.

Beautify Files

I'm moving from js-beautify to prettier, but don't quite want to delete this section yet. Use prettier instead of js-beautify because it handles JSX much better.

Before we had prettier, we used js-beautify, but not on all files in a directory. Create a script called beauty with this content:

#! /bin/bash

find . -iname '*.js' | grep -vFf skip | xargs js-beautify -r

In the above code, skip is a text file containing a list of files or directories that you want to ignore. For instance the file might contain a list like this:


Both beauty and skip might go in the root of a project or the root of your repository.

Alternatively, you could do this:

find . -iname *.js -type f -not -path '**/node_modules/**' -not -path '**/bundle.js' -not -path '**/registerServiceWorker.js' -print0 | xargs -0 js-beautify -r