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Asyncjs : Bypass a function in a waterfall chain

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[前端(javascript) 所属分类 前端(javascript) | 发布者 店小二05 | 时间 2019 | 作者 红领巾 ] 0人收藏点击收藏

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 !

Problem courtesy of: manuquentin

Solution

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 });

Solution courtesy of: bevacqua

Discussion

I would recommend using clojurescript which has an awesome core-async library which makes life super easy when dealing with async calls.

In your case, you would write something like this:

(go (when-let [res1 (<! (asyncFunc1))] (<! (asyncFunc2 res1))) (<! (asyncFunc3)))

Note the go macro which will cause the body to run asynchronously, and the <! function which will block until the async functions will return.

The code will first block on the first async function. Then, if the result of that is true, it will run the second async function on block on that as well. Lastly, it will run the third async function and block on that.

Discussion courtesy of: Asher

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

Discussion courtesy of: Yaniv Kessler

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 )

Discussion courtesy of: Alejandro Silva

This recipe can be found in it's original form on Stack Over Flow .

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