Good Refactoring vs Bad Refactoring

The author mentions that some of the changes broke things, but it's a long way into the article before the word "test" appears. It's only point 6/7 of his recommendations.

Making changes with no test coverage is not refactoring. It's just rewriting. Start there.

I largely agree with this nodding along to many of the pitfalls presented. Except numbers 2s good refactor. I hope I won't sound too harsh/picky for an example that perhaps skipped renaming for clarity on the other parts, but I wanted to mention it.

While I don't use javascript and may be missing some of the norms and context of the lanugage, creating lamda functions (i don't know the js term) and then hardcoding them into a function is barely an improvement. It's fine because they work well with map and filter, but it didn't address the vague naming. Renaming is refactoring too!

isAdult is a simple function with a clear name, but formatUser and processUsers are surprisingly vague. formatUser gives only adult FormattedUsers, and that should probably be highlighted in the name of formatUser now that it is a resuable function. To me, it seems ripe for mistaken use given that it is the filter that at a glance handles removing non-adult users before the formatting, while formatUser doesn't appear to exepct only adult users from it's naming or even use! Ideally, formatUser should have checked the age on it's own and set isAdult true/false accordingly, instead of assuming it will be used only on adult Users.

Likewise, the main function is called processUsers but could easily have been something more descriptive like GetAdultFormattedUsers or something similar depending on naming standards in js and the context it is used in. It may make more sense in the actual context, but in the example a FormattedUser doesn't have to be an adult, so a function processing users should clarify that it only actually creates adult formatted users since there is a case where a FormattedUser is not an adult.

1. Changing the coding style substantially

Well refactoring is the only place you can change the coding style... But really a change to the coding style should not be done blindly, but with by in from team before you start changing it. It is not uncommon for a team to make bad decisions throughout the course of a project, including the style they picked. And if you ask around you might find others have the same idea as you and don't like the current style. Then you can have a conversation about it. But you should not jump in and start changing the style of a code base before you talk to your team.

One of the biggest problems I've seen is refactoring code while learning it, in order to learn it. This is a terrible idea. I've seen comments that you should work with a given piece of code for 6-9 months. Otherwise, you are likely to create bugs, hurt performance, etc.

I disagree with this. No refactoring for 6 to 9 months? That is just insane. IMO refactoring is a great place to learn how the code works. But it does need review of someone more experience to see if you are missing anything important. They can then point out why those bits are important and you just learned a bit more about the code base.

If no one else knows then what is 6 to 9 months going to achieve? The lesson here is to not refactor blindly, but to seek out others that understand the code before you refactor, and failing that spend more time trying to understand it before refactoring.

6. Overly consolidating code

Another way to put this is don't overly DRY your code. And here I would stick with the original code, not either refactor. It saves no lines and just makes the lines far longer. So much so it gives my a horizontal scrollbar on it...

But overall there are some good ideas in the post. Though I do dislike how they are using the term refactoring. All of these apply to any code you write, not just refactoring existing code.

SEO breaks the web, writer was a hero :)

I appreciate that this article highlights the value of using of named functions in functional-style code. Too often, programmers assume that "functional programming" means using lambdas everywhere, when in my experience, lambdas are actually a (very mild) code smell.