How to execute a set of async tasks in nodejs in a loop?

Question

I want to perform a set of async tasks repeatedly in a loop. I tried using async library's waterfall approach to do something like

while(somethingIsTrue) {
     async.waterfall([
         function(callback) { ... },
         function(callback) { ... },

     ], function(err) {
         ...
        }
     );
}

The problem I encountered was that the the first async function never got scheduled or rather executed and the loop kept on running, obviously because the loop didnt wait for the async functions to finish. I'm not so well verse with asynchronous programming and I would need help to come up with some pattern to solve this problem.

user663031 · Accepted Answer · 2015-06-24 07:18:34Z

1

Try a semi-recursive solution such as

function again_and_again(callback) {
    if (!somethingIsTrue) return;
    async.waterfall([
         function(callback) { ... },
         function(callback) { ... },
    ], function(err, result) {
        if (err) return callback(err);
        again_and_again(callback);
    });
}

The idea is to wait for the waterfall to finish, and arrive at the callback, and repeat the "loop" there by calling again_and_again again.

answered Jun 24, 2015 at 7:18

user663031

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1 Comment

robertklep Over a year ago

Alternatively, async#whilst might also be useful.

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