gulpfile.js

const {
  task,
  watch,
  src,
  parallel,
} = require('gulp');
const eslint = require('gulp-eslint');
const cache = require('gulp-cached');
const { spawn } = require('child_process');

const { log } = console;

let node;
const entry = 'src/index.js';
const lintPaths = ['src/**/*.js', 'scripts/**/*.js'];
const watchPaths = ['src/**/*.js', 'scripts/**/*.js'];

const serve = async () => {
  if (node) node.kill();
  node = await spawn('node', [entry], { stdio: 'inherit' });
  node.on('close', (code) => {
    if (code === 8) {
      log('Error detected, waiting for changes...');
    }
  });
};

const lint = () => src(lintPaths)
  .pipe(cache('lint'))
  .pipe(eslint())
  .pipe(eslint.format());

task('default', () => {
  watch(
    watchPaths,
    { queue: false, ignoreInitial: false },
    parallel([serve, lint]),
  );
});