TypeScript Survival Guide: Life-Saving Tips and Techniques

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Let's go through your survival kit for the TS jungle! In this talk, you'll get the complete TS guide from simple tips to complex techniques that will help you take the most of TypeScript not only in those large production projects, but also in your small hobby idea. We'll explore validations, configuration, typings and much more.

Lucas Santos
Lucas Santos
7 min
21 Sep, 2023

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Video Summary and Transcription

Hello, I'm Lucas, a software engineer at Klarna in Sweden. I will be sharing my best tips and tricks with TypeScript. One useful tool is tsconfig-basis, which eliminates the need for copying and pasting the same tsconfig file. Rendered types in TypeScript are powerful for handling different types of strings, and type guards and assertion functions make them even more useful. Enums in TypeScript can be number, string, or const, each with its own advantages and limitations. Lastly, there are new features in PS 5.2 like 'using' for resource disposal and 'unknown' for data protection, as well as a case conversion utility type for interfaces.

1. Introduction to TypeScript and tsconfig-basis

Short description:

Hello, I'm Lucas. I'm a software engineer here at Klarna in Sweden. I will be presenting the best tips and tricks that I've learned with TypeScript in these past years with you. First thing, over the past few years, I lost how many times I have copied and pasted the same tsconfig over and over again, until I discovered that I could just use tsconfig-basis. It's an official repository that has several tsconfig-basis for you to extend naturally.

Hello, I'm Lucas. I'm a software engineer here at Klarna in Sweden. I'm originally from Brazil and have been coding for the past 11 years and sharing what I learned. So if you like this talk and have any feedback, please reach out to me and my socials, just put the name of the network in elsantos.dev and you'll get there, or just elsantos.dev will also do the trick.

But cutting to the chase, I will be presenting the best tips and tricks that I've learned with TypeScript in these past years with you. And all of this in 10 minutes or less. So, let's go.

First thing, over the past few years, I lost how many times I have copied and pasted the same tsconfig over and over again, until I discovered that I could just use tsconfig-basis. It's an official repository that has several tsconfig-basis for you to extend naturally. And tsconfig supports that through the extends property. So, as you can see, we can use the extends and pass the name of the repo following the configuration that we want to extend. And if you don't like any of those configs, you can just override it by writing it again in the bottom. But this is not only for the tsconfig-basis extension. So, you can actually extend if you have local files, if you want to extend, like in a mono-repo configuration where you need to extend the base file. So, what you can do is you just need to put that path in that file, and it's magic. So, you never have to copy a tsconfig again.

2. Rendered Types and Type Guards

Short description:

Rendered types in TypeScript are powerful for handling different types of strings. They allow you to mark a string as a specific type, such as an ID, preventing mistakes like passing a name to an ID. However, rendered types require explicit type casting, which can be cumbersome. To overcome this, we have type guards and assertion functions. Type guards allow us to narrow down the type without explicit casting, while assertion functions throw errors if the type is incorrect. This makes rendered types more useful and allows for lightweight guards.

For the second tip, I wanted to something that took me some time to understand how powerful it actually was. I'm talking about rendered types. Normally, you don't see a lot of those in TS Code. That's because they have a very specific use case. And those are massively helpful when you have different types of strings, but still strings, like a uid. You can render type to mark it as an ID, even though it's a string. But it's a string of a certain type, making it impossible to pass a name to an ID by mistake, for example. Or even to pass the wrong type of ID to some function.

However, rendered types can only be converted to explicit type casting, which is bad, so we can make a function to explicitly convert one type into another. But it's still, there's a better way to do this. And I present to you the third survival tip, the type guards and assertion functions. When you use rendered types, they are usually followed by one of those two. Because guards and assertion allows us to narrow down the type without having to explicitly cast it. I can explicitly cast anything to an ID and it's going to work, basically. The trick here is basically to add a new function that will guard the type, and this function is saying that a type is of another type as a return annotation. This way, we can do an if check and actually check the ID is an id with the rejects. But this is not just adding noise, this if there. I don't like it. This is why we have assertion functions. They are declared by saying that the function asserts a parameter of a given type. So, the main difference between one and the other is that the assertion functions don't return anything they throw, while the guards return booleans. So, this way, rendered types can be more useful, and you can also create guards that are lightweight.

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