How to Create a Function to Receive Keyboard Input in JavaScript (nodejs) Without HTML

Question

I'm trying to get an input from the keyboard by calling a function that uses the built-in readline module, but it seems that the loop "doesn't wait" for each function call to finish.

The main function is supposed to print the 4 different numbers that are inputted.

I've tried using async-await on my main function, but that had the same result. Is async-await even needed for this?

I'm using the command node input.js in terminal to run the program. No HTML.

function getInput(question) {
  var readline = require('readline');

  var rl = readline.createInterface({
      input: process.stdin,
      output: process.stdout
  });
  rl.question(question, function (x) {
    var aString = parseInt(x);
    rl.close();
    entered = true;
    return aString;
  });

}

async function main() {
  var i = 0;
  var myGuess;
  while (i <= 3) {
    myGuess = await getInput("Enter something: ");
    console.log(myGuess);
    i++;
  }
}
main();

I expect to see:

Enter something: 3 // just entering random numbers
3
Enter something: 9
9
Enter something: 12
12
Enter something: 55
55

But I get:

Enter something: undefined
Enter something: undefined
Enter something: undefined
Enter something: undefined
2222                         // I only got to enter 2...

xiantank · Accepted Answer · 2019-05-24 03:05:15Z

1

read how to use await

The await operator is used to wait for a Promise. It can only be used inside an async function.

  return new Promise((resolve, reject) => {
    rl.question(question, function (x) {
      var aString = parseInt(x);
      rl.close();
      entered = true;
      return resolve(aString);
    });
  });

answered May 24, 2019 at 3:05

xiantank

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