In NodeJS how do I exit a parent function from a virtual function

Question

I have something like the following

var async = require(async)

function start () {
    async.series(
        [
            function (callback) {
                // do something
                callback(null, "Done doing something")
                return // EXIT start() NOT JUST THIS VIRTUAL FUNCTION
            },
            function (callback) {
                // do something else if the first thing succeeded
                callback(null, "Done doing something else")
            }
        ],
        function (err,result) {
            if (err) {
                console.log(err)
            }
        }
    )

    console.log("All done!")
}

// Start doing stuff
start()

Is it possible to exit the function start() based on some condition from within the contained virtual function where I placed the comment "EXIT start() NOT JUST THIS VIRTUAL FUNCTION"

Answer 1

In short yes, you can exit the task series early. async uses error-first callbacks, which are a fundamental async callback structure in Node.js. An additional resource for learning about Async development using Node.js see this great blog post from RisingStack.

Callbacks from async get returned to a final callback that is called when the async.series is completed if supplied, this callback is optional. If a task within the series returns the callback with a value other than null in the first parameter, the error parameter, the series will break and return to the final callback handler.

async.series(
    [
        function (callback) {

            // If some condition is met, exit series with an error
            if (someCondition)
                return callback('exit start', null);

            return callback(null, 'Done doing something');
        },
        function (callback) {
            if (someCondition)
              return callback('error', null);

            // do something else if the first thing succeeded
            return callback(null, "Done doing something else")
        }
    ],
    function (err,result) {
        // Handle error returned from a series callback if one occurred      
        if (err) {
            console.log(err)
        }
    }
)