Nested loops using async.js

Question

I want to do a very simple code, where I have two nested loops in javascript that print out the index they are currently on. (it's the base for something else i want to do). The inner loop has a timer, so it should wait 1 second before printing each number.

I would expect this output:

outer count: 0
inner count: 0
inner count: 1
inner count: 2
inner count: 3
inner count: 4
in out 
outer count: 1
inner count: 0
inner count: 1
inner count: 2
inner count: 3
inner count: 4
in out

etc, but this is not happening. Is there some obvious mistake in my code? can async whilst functions even be nested? please help! :(

This is my code so far:

var count = 1;
        async.whilst(
        function() {return count < 5},
        function(callback){


            var icount = 0;

            console.log("outer count:" + count);

            async.whilst(
                function () { return icount < 5; },
                function (callback) {
                    console.log("inner count:" + icount);
                    icount++;
                    setTimeout(callback, 1000);
                },
                function (err) {
                    // 5 seconds have passed
                    console.log("in out");
                }
            );

            count++;

            callback();

        },
        function(err){
            console.log("out out");
        }
        );

Call callback in the asynchronous callback?

Bergi
– Bergi

2015-08-21 01:08:25 +00:00
Commented Aug 21, 2015 at 1:08 — Bergi
– Bergi, Commented Aug 21, 2015 at 1:08

zerkms · Accepted Answer · 2015-08-21 01:02:17Z

5

var count = 1;
        async.whilst(
        function() {return count < 5},
        function(outer_callback){


            var icount = 0;

            console.log("outer count:" + count);

            async.whilst(
                function () { return icount < 5; },
                function (callback) {
                    console.log("inner count:" + icount);
                    icount++;
                    setTimeout(callback, 1000);
                },
                function (err) {
                    // 5 seconds have passed
                    console.log("in out");
                    outer_callback(); // <--- here
                }
            );

            count++;


        },
        function(err){
            console.log("out out");
        }
        );

async.whilst is not blocking, which means that all 5 of them are scheduled to run simultaneously.

The change I made is that now in the code the outer loop iteration is only completed as inner loop iteration is done.

answered Aug 21, 2015 at 1:02

zerkms

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1 Comment

user2107435 Over a year ago

i have found a bug in this answer i put here fix code :

user2107435 · Accepted Answer · 2016-06-16 14:36:44Z

0

Nested loops using async.js :

    var i = 0;
    async.whilst
    (
        function() {return i < 3},

        function(next_i)
        {
            var j = 0;
            async.whilst
            (
                function () { return j < 3; },
                function (callback) 
                {
                    console.log( i +' / '+ j);
                    j++;
                    setTimeout(callback,0);
                },
                function () 
                {
                    i++;
                    next_i();
                }
            );
        }
    );

console.log

answered Jun 16, 2016 at 14:36

user2107435

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