Using ESLint in a script

August 29th, 2018. Tagged: JavaScript

Instead of running ESLint on the command line and passing files to it, I wanted to require() and use it with code from strings. That is because I want to lint and unit-test the code from the book I write in AsciiDoc. (Will post the complete script once it's running properly, some taste)

Had to jump through a few hoops, so here it is for the posterity (where posterity = me, next month)

Install

$ npm install eslint --save-dev

Create a configuration file

This one always trips me up. ESLint's binary has an `--init` option now that takes care of this and I tried it, but the generated "standard" file was missing rules, etc, so I abandoned the idea in favor of creating am .eslintrc.json file in my directory with this content:

{
    "extends": [
        "eslint:recommended"
    ]
}

The code

const CLIEngine = require('eslint').CLIEngine;
const cli = new CLIEngine({
  parserOptions: {
    ecmaVersion: 6,
  },
  rules: {
    'no-unused-vars': 'off',
  }
});

const report = cli.executeOnText("let foo = 'bar';;").results[0];

if (report.errorCount) {
  console.log(report.messages);
} else {
  console.log('No errors');
}

In action:

ESLint script in action

A note about the two config options passed to the constructor:

  • parserOptions lets me use more modern syntax
  • rules is just an example of how to zap some rules

Happy ESLinting!

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