ESLint

ESLint is an extremely flexible, unopinionated-by-default linter for JavaScript. You configure linter rules in a .eslintrc file at the root of your project. ESLint can be run before (or as part of) your tests to ensure that your project standards are followed. In addition, you can configure your editor to run the rules, helping you avoid common mistakes and conform to coding standards as you develop.

eslint-config-planet

The eslint-config-planet package is a shared ESLint configuration that suggests rules for all Planet web development projects. You can install the shared configuration and ESLint with the following:

npm install --save-dev eslint eslint-config-planet

After that, add a .eslintrc file to the root of your project that looks like this:

{
  "extends": "planet"
}

If there are rules that you cannot follow (or otherwise disagree with), you can override them in your .eslintrc file. For example, if you want your project to allow mixed quotes (instead of enforcing single quotes), your .eslintrc could look like this:

{
  "extends": "planet",
  "rules": {
    "quotes": 0
  }
}

(This turns off the quotes rule.)

See the eslint-config-planet readme for more detail on the available profiles. And please submit a pull request if there is a new profile that you think would be worth supporting.

Running the linter

After installing and configuring ESLint, you'll want to run it on your JavaScript source files. Since you've got a locally installed version of eslint, a good way to run it is by adding a package.json script - all locally installed binaries are available on your path when running an npm script.

If you don't already have any tests for your project, the first thing you might want to do is run the linter as a testing step. You can do this by adding the following to your package.json:

  "scripts": {
    "test": "eslint src"
  }

Now you can run the linter on all the files in your src directory like this:

npm test

As you add real tests to your project, you can move linting to a "pretest" script. For example, assuming you use mocha to run your tests, your package.json scripts might look like this:

  "scripts": {
    "pretest": "eslint src",
    "test": "mocha"
  }

Now npm test will run the inter first, and if that succeeds, mocha will run next.

Editor configuration

You can set up your editor to run ESLint as you develop. See the editors page to find detail on configuring your favorite editor.