In your Haraka plugin:

1. Add to NPM dependencies: npm install --save-dev eslint eslint-plugin-haraka

2. Install an eslint config file:

tee .eslintrc.yaml <<EOLINT
plugins: [ haraka ]
extends: [ eslint:recommended, plugin:haraka/recommended ]
EOLINT

3. Add within the "scripts" section of package.json:

"lint": "npx eslint *.js test/*.js"
"lintfix": "npx eslint --fix *.js test/*.js"

4. Add to the "script" section of .travis.yml:

npm run lint

To check your project against lint rules:

npm run lint

Step #4 above does this automatically when CI tests are set up.

If you agree with the lint suggestions, you can run npm run lintfix and the changes will be made to your files automatically.

If you disagree, you can add custom rules to your .eslintrc file.