Script takes the port as a param and tries to find and kill a process which is listening the port, e.g. `node killProcessByPort.js 8080`

killProcessByPort.js

#!/usr/bin/env node

/**
 * Script takes the port as a param and tries to find and kill a process
 * which is listening the port
 *
 * Example of the script usage:
 * node SCRIPT %PORT_NUMBER%
 */

// VARS
const port = process.argv[2]; // taking line argument
if (!port) {
    throw new Error('The script expects the port number sent via param');
}

// HELPERS
/**
 * Executes the command with the arguments
 * @param cmd {String}
 * @param args {String}
 * @param callback {Function}
 */
function runExecCommand(cmd, args, callback) {
    exec(
        `${cmd} ${args}`,
        (err, stdout/*, stderr*/) => {
            if (err) {
                callback(1, err);
            } else {
                callback(0, stdout);
            }
        });
}

function killPyPort({
    getPIDByPortCommand,
    getKillCommandFromOutput
}) {
    // execute the find PID command
    return runExecCommand(
        getPIDByPortCommand,
        '',
        (code, data) => {
            if (code !== 0) {
                console.error(`Couldn't find a process on the port: ${port}`, data);
                return;
            }

            if (!data) {
                console.log(`Couldn't find a process on the port: ${port}`);
                return;
            }

            // execute the kill command
            runExecCommand(
                getKillCommandFromOutput(data),
                '',
                (_code, _data) => {
                    if (_code !== 0) {
                        console.error(`Couldn't kill a process on the port: ${port}`, _data);
                        return;
                    }

                    console.log(`Done`);
                }
            );
        }
    );
}

// INIT
if (process.platform === 'win32') {// WINDOWS
    // http://stackoverflow.com/a/35312370
    killPyPort({
        getPIDByPortCommand: `echo off & (for /f "tokens=5" %a in ('netstat -aon ^| findstr ${port}') do echo "%a") & echo on`,
        getKillCommandFromOutput: (output) => {
            const PID = output.split('\n')[0];// the first line only
            return `taskkill /F /PID ${PID}`;
        }
    });
} else {// NON WINDOWS
    // http://stackoverflow.com/a/16583477
    killPyPort({
        getPIDByPortCommand: `lsof -P | grep ':'${port} | awk '{print $2}'`,
        getKillCommandFromOutput: (output) => {
            //noinspection UnnecessaryLocalVariableJS
            const PID = output;// output is the PID actually
            return `kill -9 ${PID}`;
        }
    });
}