This script kills applications that are running on a given port

killport.js

#!/usr/bin/env node

const { exec } = require('child_process')

const findNumber = arg => !isNaN(parseInt(arg, 10))

const port = process.argv.find(findNumber)

const execCommand = command =>
  new Promise((resolve, reject) =>
    exec(command, (err, stdout, stderr) =>
      err ? reject(err) : resolve({ stdout, stderr })
    )
  )

execCommand(`kill -9 "$(lsof -t -i:${port})"`)
  .then(
    () => (
      console.log(`Application on port ${port} was killed`), process.exit(0)
    )
  )
  .catch(
    () => (
      console.log(`There's no application running on port ${port}`),
      process.exit(1)
    )
  )