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

# Overview

When trying to eliminate `any` from your codebase, it's useful to know about the `unknown` type. It is a safer alternative to `any`. Both `any` and `unknown` represent an unknown type. However, there is a key difference between these two:

* all types are assignable to the `any` type and the `any` type is assignable to any other type 
* all types are assignable to the `unknown` type, but the `unknown` type is not assignable to any type 

# Type assignability

What does it mean when a type is assignable to another type? We say that type `A` is assignable to type `B` if you can use a value of type `A` in all places where a value of type `B` is required. 

Here are some examples of situations when type assignability is checked:

* assigning a value to a variable
* passing a function argument
* returning a value from a function that has an explicit return type

As mentioned, the key difference between `any` and `unknown` is that `any` is assignable to any other type, but `unknown` is not assignable to any type. Let's look at some examples.

This lesson explains the `unknown` type and explains how it is a better alternative to using `any`.

Strict types

Generics

Composing types

Advanced types

TypeScript in practice

Conclusion

The `unknown` Type

Overview

Type assignability