const childProcess = require("child_process");

const readWholeStream = (...streams) => new Promise((res, rej) => {
    const allBuffer = [];
    let running = streams.length;
    for (const stream of streams)
        stream
            .on('data', buffer => allBuffer.push(buffer))
            .on('end', () => --running == 0 ? res(Buffer.concat(allBuffer)) : null)
            .on('error', err => rej(err));
});

const getOutput = async childProcess => {
    const stdout = readWholeStream(childProcess.stdout);
    const stderr = readWholeStream(childProcess.stderr);
    const combined = readWholeStream(childProcess.stdout, childProcess.stderr);

    return {
        stdout: (await stdout).toString('utf8'),
        stderr: (await stderr).toString('utf8'),
        combined: (await combined).toString('utf8')
    }
}

const executeCommand = async command => {
    const proc = childProcess.spawn(command[0], command.slice(1));

    const outputProm = getOutput(proc);
    const exitCodeProm = new Promise((res, rej) => proc.on('exit', res));

    const output = await outputProm;
    const exitCode = await exitCodeProm;

    return {
        ...output, exitCode,
        hasErrord: exitCode != 0 || output.stderr != ''
    }
}

(async () => {
    console.log(await executeCommand(['node', 'example.js']));
})();