How can I use command prompt inside my code, with node.js?

Here is a small example to use child_process.

Execute command in cmd.

const { exec } = require("child_process");

function os_func() {
    this.execCommand = function(cmd, callback) {
        exec(cmd, (error, stdout, stderr) => {
            if (error) {
                console.error(`exec error: ${error}`);
                return;
            }

            callback(stdout);
        });
    }
}

app.get("/", (req, res) => {
    console.log("inside get");
    var os = new os_func();
    os.execCommand('arp -a', function (returnvalue) {
      res.end(returnvalue)
});

});

There is a global function i.e: process.argv

Or if you want to take command-line arguments a lot better try npm package yargs.