Javascript iteration using while loop issue

Question

I am trying to create a loop where I can keep prompting myself question while not exiting the loop until I enter 1. however it is not working at the moment, any advise?

var prompt = require('prompt');             //require to use prompt
var sync = require('sync');                //require to use synchronous function

var choice = 0;

sync(function()
{
while(choice != 1)
{
    if(choice == 0)
    {

        prompt.start();

        prompt.get(['message'], function(err, result)
        {
            if (err)
            {
                return onErr(err);
            }
            data(result.message);
            choice = result.message;
        });

    }
    else if (choice == 1)
    {
        break;
    }
}
});

The callback you pass to prompt.get() never has a chance to run because the while is blocking the job queue. Learn about run to completion: developer.mozilla.org/en-US/docs/Web/JavaScript/… . — Felix Kling
– Felix Kling, Commented Mar 17, 2016 at 4:33
I suggest you use the debugging technique of executing this in your head. — user663031
– user663031, Commented Mar 17, 2016 at 4:33
Assuming you are just starting with node, you should learn how to use callbacks (and make a recursive solution instead of the while loop). — Bergi
– Bergi, Commented Mar 17, 2016 at 4:34
If you're really determined to use sync, you should check again its docs. You'd need to call var result = prompt.get.sync(['message']). — Bergi
– Bergi, Commented Mar 17, 2016 at 4:35

Lukasz Wiktor · Accepted Answer · 2016-03-17 04:39:00Z

1

Classic loops don't play well with async code. You need another approach:

var prompt = require('prompt');

prompt.start();

function read() {
    prompt.get(['message'], function(err, result) {
        if (err) {
            return onErr(err);
        }
        console.log(result.message);
        if (result.message != 1) {
            read();
        }
    });
}

read();

answered Mar 17, 2016 at 4:39

Lukasz Wiktor

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