Asyncjs : Bypass a function in a waterfall chain

Question

Asyncjs : Bypass a function in a waterfall chain

I want to jump a function from a chain of waterfall functions with asyncjs in nodejs.

My code look like this :

async.waterfall([
    function(next){
        if(myBool){
            next(null);
        }else{
            // Bypass the 2nd function
        }
    },

    // I want to bypass this method if myBool is false in the 1st function
    function(next){
    },

    // Always called
    function(next){
    }
]);

Do you know a proper way to do this without put :

if(!myBool){
    return next();
}

In the function I want to bypass.

Thanks !

node.js
asynchronous
callback
waterfall

Answer 1

An alternative might be:

var tasks = [f1];

if(myBool){
    tasks.push(f2);
}

tasks.push(f3);

async.waterfall(tasks, function(err, result){
});

where f1, f2, and f3 are your functions.

other than that, you're better off doing it explicitly, avoid making your code overly complicated, simpler is usually better

update:

function f1(done){
    if(myBool){
        f2(done);
    }else{
        done();
    }
}

function f2(done){
    async.nextTick(function(){
        // stuff
        done();
    });
}

async.waterfall([f1,f3],function(err,result){
    // foo
});

Answer 2

I think this should work:

var finalCallback = function(err, result){
  if(err)
     // handle error..
  else
     console.log('end! :D');
}

async.waterfall(
  [
    function step1(callback){
       // stuff
       callback(null, someData);
    },
    function step2(someData, callback){
       if(skip_step_3)
          finalCallback(null, someData);
       else
          callback(null, someData);
    },
    function step3(moreData, callback){
       // more stuff
       callback(null, moreData);
    }
  ],
  finalCallback
)

the creator of async recomend this in the github repo (https://github.com/caolan/async/pull/85)

Answer 3

Using if-async module your code will look like this:

var async = require('async')
var ifAsync = require('if-async')

async.waterfall([
    foo,
    ifAsync(p1).then(c1).else(c2),
    bar
], function(err) {})

for full example take a look here: https://github.com/kessler/if-async#example-2-using-with-asyncjs-waterfall