Now consider we want to handle numbers in our known value set: const KNOWN_VALUES = Object.freeze(['a', 'b', 'c', 1, 2, 3]) function isKnownValue(input?: string | number) { return typeof(input) === 'string' && KNOWN_VALUES.includes(input) } Uh oh! This TypeScript compiles without errors, but it's not correct. Where as our original "naive" approach would have worked just fine. Why is that? Where is the breakdown here? It's because TypeScript's type system got in the way of the developer's initial intent. It caused us to change our code from what we intended to what it allowed. It was never the developer's intention to check that input was a string and a known value; the developer simply wanted to check whether input was a known value - but wasn't permitted to do so.

Have you ever felt like a framework was getting in the way instead of helping you go faster? Maybe you’re stuck on some simple task that would be easy to do manually, but your framework is making you jump through configuration hoops. I end up getting lost in a sea of documentation (or no documentation), and the search for that one magical config key takes just a tad bit too long. It’s a productivity sink, and worse than the time delay it adds to my frustration throughout the day.

However, especially when starting out, it’s very easy to fall into the “this is how I did things in my previous framework” trap.