callback

[aIbrahiim]

Hello Geeks, could you please tell me how to master callback and callback hell ?

[gireeshpunathil]

a detailed explanation on the event driven programming is available here: #1118 . If you have doubts on any specific area(s) please let me know.

callback hell is a meme and is neither defined nor documented within Node.js project. The wording originates from complete or partial inability to follow the control flow when large ( more than 3) number of callbacks are connected together. The perceived lack of readability and associated potential program(mer) error is generally referred to as callback hell.

Primary use case for callback is completion handing of an I/O work that happens asynchronously. While this is pervasively used in Node programs, chaining such callbacks deeply is not a common thing, and I am yet to see a real use case where more than 10 callbacks chain up to complete a common business logic. There could be one or two, but then those would probably the central part of an application (such as the composition layer of a webapp that follows microservice architecture) and would be carefully developed and reviewed with control flow well tested.

The meme largely come from programmers from other languages who perceive code sequences to be executed in the order in which those were written.

Promise is a way to circumvent callback chaining. Promise do not avoid callbacks, instead they hide the visibility of the chaining from the user program.

Usage of promise in large scale production systems may degrade overall performance.

[aIbrahiim]

Thanks Sir,How can I improve my skills in node.js and Expressjs ? how can I practise on them ?

[gireeshpunathil]

are you willing to be active in the community? then there are a number of things I can suggest:

• node.js doc: https://nodejs.org/dist/latest-v10.x/docs/api/ [ this gives an idea about what are the Node.js APIs ]
• node.js test suite: https://github.com/nodejs/node/tree/master/test [ this gives an idea about how the APIs are used
• https://github.com/nodejs/node/labels/good%20first%20issue [ this gives a list of items one of which you can start reviewing and see if you can work on it ]

Expressjs is not part of Node.js project, so I cannot comment on that.

Good luck!

[aIbrahiim]

Thanks so much I really appreciate that.
Does nodejs is good path to work as web developer in big companies like in europe or usa ?

[gireeshpunathil]

ah! although it is an honest and awesome question, I cannot answer it, something that influences your career decision.

However, I will copy @nodejs/community-committee to chime in and advise, assuming they are best placed to respond to that within this project.

If there is anything more on technical help and support, I am happy to assist! thank you.

[Bamieh]

@Woodyinho I suggest that you take a look at the Node.js user survey report which will give you a general overview about the users of Node.js and understand how they use it.

To get a hint about the companies that use Node.js and the positions they are seeking, take a look at Stackshare's "companies using Node.js" section.

Finally, Stackoverflow's 2018 user survey report will give you a general overview about the place of node in the overall market, average salaries, positions, and how users rank it in comparison to other technologies and platforms.

I hope you find this helpful while still unbiased, Cheers!

[gireeshpunathil]

Closing as answered.