1-cps.js

/* Continuation Passing
 * Written in node pre-ES6 style */
var readline = require("readline");
var userId = "blarg";
var rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});

rl.question("Please re-enter the userId", confirmUserId);

function confirmUserId(answer) {
    if (answer !== userId) {
        console.error("Wrong userId provided");
        process.exit(1);
    }

    rl.question("Confirm (y) or (n)", confirmQuestion);
}

function confirmQuestion(answer) {
    if ("y" === answer) {
        console.log("Completed confirmation");
    }
    else {
        console.log("You did not confirm");
    }
    rl.close();
}

2-promise.with-callbacks.js

/* Using promises
 * Written in node pre-ES6 style */
var Promise = require("bluebird");
var readline = require("mz/readline");
var userId = "blarg";
var rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});

rl.question("Please re-enter the userId").then(function (answer) {
    if (answer !== userId) {
        console.error("Wrong userId provided");
        process.exit(1);
    }

    return rl.question("Confirm (y) or (n)");
}).then(function (answer) {
    if ("y" === answer) {
        return console.log("Completed confirmation");
    }
    console.log("You did not confirm");
}).then(rl.close.bind(rl));

3-promise-with-callbacks.es6

/* Using promises
 * Written in ES2015 style */
const readline = require("mz/readline");
const userId = "blarg";
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});

rl.question("Please re-enter the userId").then(answer => {
    if (answer !== userId) {
        console.error("Wrong userId provided");
        process.exit(1);
    }

    return rl.question("Confirm (y) or (n)");
}).then(answer => {
    if ("y" === answer) {
        return console.log("Completed confirmation");
    }
    console.log("You did not confirm");
}).then(() => rl.close());

4-co.js

/* Using co
 * Written in ES2015 style */
const readline = require("mz/readline");
const co = require("co");
const userId = "blarg";
const rl = readline.createInterface({
    input: process.stdin,
    output: process.stdout,
});

co(function* () {
    let answer = yield rl.question("Please re-enter the userId");
    if (answer !== userId) {
        console.error("Wrong userId provided");
        process.exit(1);
    }

    answer = yield rl.question("Confirm (y) or (n)");

    if ("y" === answer) {
        return console.log("Completed confirmation");
    }
    console.log("You did not confirm");
}).then(() => rl.close());

package.json

{
  "name": "foo",
  "version": "1.0.0",
  "description": "",
  "main": "i.js",
  "scripts": {
    "test": "echo \"Error: no test specified\" && exit 1"
  },
  "author": "",
  "license": "ISC",
  "dependencies": {
    "bluebird": "^3.0.6",
    "co": "^4.6.0",
    "mz": "^2.1.0"
  }
}