.eslintrc.js

module.exports = {
  env: { browser: true },
  extends: ['eslint:recommended', 'plugin:compat/recommended'],
};

index.js

function test(string) {
  if (!string.startsWith('http')) {
    // expecting error - but none
    return false;
  }

  return true;
}

test('ok');

package.json

{
  "name": "compat-test",
  "version": "1.0.0",
  "description": "",
  "main": "index.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "keywords": [],
  "author": "",
  "license": "ISC",
  "devDependencies": {
    "babel-eslint": "^8.2.3",
    "eslint": "^4.19.1",
    "eslint-plugin-compat": "^2.4.0",
    "eslint-plugin-react": "^7.9.1"
  }
}