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Author Archives: Jakub Holy

Jakub is an experienced Java[EE] developer working for a lean & agile consultancy in Norway. He is interested in code quality, developer productivity, testing, and in how to make projects succeed.

Beware the performance cost of async_hooks (Node 8)

I was excited about async_hooks having finally landed in Node.js 8, as it would enable me to share important troubleshooting information with all code involved in handling a particular request. However it turned out to have terrible impact of our CPU usage (YMMV):                 This was quite extreme and is likely related to ...

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WTF code, defects, and the principle of least astonishment

We have recently introduced two defects, while trying to improve old, obscure code. Of course we are to blame for not being more paranoid and not researching more why the code was there. But if the code was clear to start with, if it followed the least astonishment principle, the errors wouldn’t have happened. In both cases the original code provoked ...

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Declarative Beats Imperative: Transforming Data In JavaScript

The product I am working on is a fairly typical web application, based on React.js and Node.js. Its main task is to fetch data from different REST-ish services, combine them, and present them in an attractive manner to users. This data extraction and transformation – keeping only the items and properties we care about and structuring them in a way ...

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Let the API Do the Hard Work: Promises in JavaScript with Q

Today’s lesson: Delegate the hard work orthogonal to your business logic – concurrency, asynchronicity, state maintenance during iteration etc. – to your language and API if you can. They are more likely to get it right and your code will be more focused on what you are actually trying to do. You should feel an unpleasant tingling when you have ...

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