Discover advanced TypeScript concepts: Gain insights into compiler flags, generic types, and discriminated unions. Delve into writing error-free code and mastering complex error messages with confidence.

typescript-3.7.5.tar.gz

TypeScript 3.7.5 Strict

TypeScript 3.7.5

Are you using TypeScript, but feel like you’re not making the most out of it? Do you find some advanced TypeScript concepts confusing? Do you get lost looking at complex type errors?

If you answered “yes” to any of these questions, then this course is for you! It introduces you to the world of advanced TypeScript concepts including: compiler flags for catching more errors, generic types, and how to compose types with discriminated unions. 

After finishing this course, you’ll feel more confident in your TypeScript skills. You will be able to write types that detect whole classes of possible runtime errors at compile time. Typing even the most untypeable JavaScript code will be a no brainer for you, and you’ll be fluent in TypeScript error messages.

Advanced TypeScript Masterclass

# Definition

The flag we're talking about is called `strictPropertyInitialization`. As usual, let's look at the definition from [the documentation](https://www.typescriptlang.org/docs/handbook/compiler-options.html). I think it's rather self-explanatory.

> Ensure non-undefined class properties are initialized in the constructor. This option requires -- strictNullChecks be enabled in order to take effect.

Enabling the flag will force you to always initialize class properties or make it explicit in the type annotation that the property can be `undefined`.

# Fixing the error

In the piece below, the `header` property produces an error because it's initialized neither in-place nor in the constructor.

This lesson introduces another compiler flag, `strictPropertyInitialization`, which brings more type safety to code that uses classes.

Strict types

Generics

Composing types

Advanced types

TypeScript in practice

Conclusion

Strict Property Initialization

Definition