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 first and the most important flag is `noImplicitAny`. Let's look at its definition from [the documentation](https://www.typescriptlang.org/docs/handbook/compiler-options.html):

> Raise error on expressions and declarations with an implied any type.

In other words, when you enable the flag, TypeScript will throw an error whenever it's impossible to infer the type of something. Without the flag, TypeScript would automatically assume that the type is `any`. With the flag enabled, you have to provide type annotation. You can still use `any`, but now you have to do this explicitly.

# `noImplicitAny` in practice 

Let's look at the example of untyped function arguments. It's not possible for TypeScript to infer their types unless you provide them with default values; so if you don't type them explicitly, it will throw an error.

This lesson introduces the `noImplicitAny` compiler flag.

Strict types

Generics

Composing types

Advanced types

TypeScript in practice

Conclusion

No Implicit `any`

Definition