As the title states, I was wondering if it is possible to use promisify (https://nodejs.org/dist/latest-v8.x/docs/api/util.html#util_util_promisify_original) for readline in node.js? I was only able to do it like this:
let data = []; const parse = () => { return new Promise((resolve, reject) => { const rl = readline.createInterface({ input: fs.createReadStream(path) }); rl.on('line', (line) => { data.push(line); }); rl.on('close', () => { resolve(data); }); }); }; Here you have a simple way to do it that doesn't use promisify:
const readline = require('readline').createInterface({ input: process.stdin, output: process.stdout }); function question(query) { return new Promise(resolve => { readline.question(query, resolve); }); } async function main() { const name = await question('Whats your name? '); console.log(`hello ${name}!`); readline.close(); } main(); 
readline = require('readline').promises.createInterface(...) and then just invoke await readline.question('...') directly, see nodejs.org/api/readline.html#class-readlinepromisesinterfaceHere is an example of how I promisify readline.question:
const rl = require('readline'); const { promisify } = require('util'); const readline = rl.createInterface({ input: process.stdin, output: process.stdout, }); // Prepare readline.question for promisification readline.question[promisify.custom] = (question) => { return new Promise((resolve) => { readline.question(question, resolve); }); }; // Usage example: (async () => { const answer = await promisify(readline.question)('What is your name? '); readline.close(); console.log('Hi %s!', answer); })(); Node (v8) documentation for custom promisified functions: https://nodejs.org/dist/latest-v8.x/docs/api/util.html#util_custom_promisified_functions
try to use bluebird which create http://bluebirdjs.com/docs/api/promise.promisifyall.html
but if the code works. then I think you don't need to promisify that since you already return it as promise.
Starting in Node 17, it's already promisified:
import { stdin, stdout } from 'node:process'; import * as readline from 'node:readline/promises'; const rl = readline.createInterface({ input: stdin, output: stdout }); const answer = await rl.question('What is your name? '); console.log('Thank you', answer); rl.close(); See the documentation:
promisify.customother types of callbacks that does not follow the pattern. For streams and event emitters you need to implement your own logic, it does share a common interface (with onclose, onfinish) but the usecases are very different.datain a higher scope than your promise, it will accumulate data for eachparseuse, if you useparsepromise 2 times, the second use will have the first values appended and then the second values also. A better approach is to set thelet datain the promise in this way for each use you will store only the new data.