Node.js synchronous prompt

user_969528 0
Viewed 17864

I'm using the prompt library for Node.js and I have this code:

var fs = require('fs'),
    prompt = require('prompt'),
    toCreate = toCreate.toLowerCase(),
    stats = fs.lstatSync('./' + toCreate);

if(stats.isDirectory()){
    prompt.start();
    var property = {
        name: 'yesno',
        message: 'Directory esistente vuoi continuare lo stesso? (y/n)',
        validator: /y[es]*|n[o]?/,
        warning: 'Must respond yes or no',
        default: 'no'
    };
    prompt.get(property, function(err, result) {                
        if(result === 'no'){
            console.log('Annullato!');
            process.exit(0);
        }
    });
}
console.log("creating ", toCreate);
console.log('\nAll done, exiting'.green.inverse);

If the prompt is show it seems that it doesn't block code execution but the execution continues and the last two messages by the console are shown while I still have to answer the question.

Is there a way to make it blocking?

node.js prompt
9 Answers

Since Node.js 8, you can do the following using async/await:

const readline = require('readline');

const rl = readline.createInterface({
  input: process.stdin,
  output: process.stdout
});

function readLineAsync(message) {
  return new Promise((resolve, reject) => {
    rl.question(message, (answer) => {
      resolve(answer);
    });
  });
} 

// Leverages Node.js' awesome async/await functionality
async function demoSynchronousPrompt() {
  var promptInput = await readLineAsync("Give me some input >");
  console.log("Won't be executed until promptInput is received", promptInput);
  rl.close();
}
user_31863670

This is dependency free, synchronous and works on Windows, Linux and OSX:

// Synchronously prompt for input
function prompt(message)
{
    // Write message
    process.stdout.write(message);

    // Work out shell command to prompt for a string and echo it to stdout
    let cmd;
    let args;
    if (os.platform() == "win32")
    {
        cmd = 'cmd';
        args = [ '/V:ON', '/C', 'set /p response= && echo !response!' ];
    }
    else
    {
        cmd = 'bash';
        args = [ '-c', 'read response; echo "$response"' ];
    }

    // Pipe stdout back to self so we can read the echoed value
    let opts = { 
        stdio: [ 'inherit', 'pipe', 'inherit' ],
        shell: false,
    };

    // Run it
    return child_process.spawnSync(cmd, args, opts).stdout.toString().trim();
}
user_770020 
const buffer = Buffer.alloc(1024);
require("fs").readSync(process.stdin.fd, buffer);
console.log(buffer.toString());
user_137338480

You can use prompt-sync

const prompt = require('prompt-sync')()

const ans = prompt('How many more times? ') // get input from the user.

P.S. prompt-sync acts weird, if prompt message contains new line character, so if you need multiline prompt just use console.log():

const prompt = require('prompt-sync')()

console.log('How many more times?\n')
const ans = prompt('') // get input from the user.
user_132123980
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