How to Pause a While Loop While Waiting for User Command-line Input?

Question

Before each loop, how can I wait for a user response before each subsequent loop?

This while loop should indefinitely take a users command-line input and add it to the sum. If the users input is -1, then it should stop the loop and return the total sum.

Unfortunately, I must use a while loop for this scenario although I know that its not the best way, its just to learn.

var userInput = 0;
var sum = 0;
const readline = require("readline").createInterface({
  input: process.stdin,
  output: process.stdout,
});

while (userInput !== -1) {
  readline.question(
    `Enter a positive number to be added to the total or -1 to end.`,
    (num) => {
      userInput = num;
      readline.close();
    }
  );
  sum += userInput;
}

@MisterJojo I mean an await in the body of a while loop. Unless you're dealing with asynchronous iterators (which readline.question is not), don't use for await … of. — Bergi
– Bergi, Commented Sep 27, 2021 at 23:53

score 1 · Accepted Answer · 2021-09-28 02:04:50Z

1

I did it, but I have almost no clue how it works!

const readline = require("readline");

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

var userInput = 0;
var sum = 0;

const numFunc = async () => {
  while (userInput !== -1) {
    const answer = await new Promise((resolve) => {
      rl.question(
        "Enter a positive number to be added to the total or -1 to end. ",
        resolve
      );
    });
    userInput = parseInt(answer);
    if (answer != -1) sum += parseInt(answer);
  }
  console.log("The sum of all numbers entered is " + sum);
  rl.close();
};

numFunc();

edited Sep 28, 2021 at 2:04

answered Sep 28, 2021 at 1:55

user14849955

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1 Comment

user14849955 Over a year ago

I learned async js, so looking back now it was just an async issue lo.

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