Determining success/failure with node.js function async.retry

Question

I'm studying the node.js module async, but I have some problems with the function async.retry.

According to its github docs, the function will continue trying the task until it succeeds or chances are used up. But how can my task tell success or failure?

I tried the code below:

var async = require('async');

var opts = {
    count : -3
};

async.retry(5, function (cb, results) {
    ++this.count;
    console.log(this.count, results);
    if (this.count > 0) cb(null, this.count);
    else cb();
}.bind(opts), function (err, results) {
   console.log(err, results);
});

I expect it to run until count === 1, but it always prints this:

-2 undefined
undefined undefined

So how can I use the function correctly?

Answer 1

You want your else-branch to fail. For that, you need to pass something to the error parameter; currently you just pass undefined which signals success - and that's what you get back.

async.retry(5, function (cb, results) {
    ++this.count;
    console.log(this.count, results);
    if (this.count > 0) cb(null, this.count);
    else cb(new Error("count too low"));
}.bind(opts), function (err, results) {
   console.log(err, results);
});