We’re going to use a simple restaurant set-menu example to explore TypeScript types. By the end of this thought-process, we’re going to be able to require one out of two members that are present on a type. Here’s the scenario. You have a set three-course menu. It looks like this: type SetMenu = { starter: […]
If you fire up a new TypeScript app and whack it into Node, you might come across the following error about The ESM Module Loader is Experimental. (dev) [email protected]:~$ node –experimental-modules run.ts (node:11333) ExperimentalWarning: The ESM module loader is experimental. (node:11333) Warning: To load an ES module, set “type”: “module” in the package.json or use […]
I have long held fast to a basic principle of letting type inference do your work for you. That means not adding type annotations unless you have a good reason to. I thought I would supply a bit more information on where to put your TypeScript type annotations and when they add value rather than […]
When TypeScript first landed in public view in October 2012, the type annotations looked a bit funky. If you were a student of type theory, they would have been familiar; but most programmers wouldn’t have seen a type annotation like this before: var name: string; Given the popularity of putting type names before variable names, […]
IntelliCode brings AI-assisted power-ups to your auto-completion. It has been in preview within Visual Studio for some time (you can read about Visual Studio IntelliCode here) – but it has now landed in Visual Studio Code, which is exceptionally handy if you’re a TypeScript programmer like me. So what is IntelliCode? It’s a simple VSCode […]
It is pretty common to want to hydrate a class from a JSON value obtained in a service. If you just parse the JSON you get the properties, but not the behaviours that you expect. As this is a reasonably common problem to solve, it is worthing doing it just once. The following function will […]
I have been working out how to create a TypeScript NotFunction type for a while, in response to a Stack Overflow question. With the arrival of conditional types, I think there may be a way. It’s not perfect – but it does work. The type works by taking all possible types and converting the type […]
The C# 8.0 announcement included a note on default implementations of interface members. If you’ve been programming for long enough, this might make you a little nervous at first thanks to the hangovers of multiple inheritance. Before you chuck out this idea, though, let’s look at it from a different perspective. I’m going to talk […]
This is one of those cases where a question keeps cropping up, so lots of people are trying to do something that the TypeScript Compiler doesn’t like very much. Yes, it’s time to talk about the TypeScript Dictarray! What’s a Dictarrary? It’s a dictionary that’s also an array. You know… one of these: const dictarray […]
Don’t worry, the mechanism for creating TypeScript mixins hasn’t changed, but I just wanted to demonstrate that the technique described in TypeScript Mixins Part Two is valid for use with static properties. Reusing the original example, let’s see what happens if we add static properties to our Flies and Climbs mixins. Not only does this […]