J. Pedro Ribeiro

Book Review: TypeScript In 50 Lessons

February 20, 2021

Typescript in 50 lessons Book Cover

I’ve started incorporating TypeScript into my daily code not too long ago. Skeptical at first, the loosely typed nature of JavaScript never bothered me as much as it does to other developers whose background on strongly typed languages is stronger.

However, mostly due to its popularity, I’ve decided to give it a go - and as you might expect, I was impressed.

After a couple of months of self learning I’ve decided to upgrade my knowledge and got my copy of TypeScript In 50 Lessons by Stefan Baumgartner.

The Book

As someone new to TypeScript, my initial thought was how accessible it is. It starts with a very hand holding approach, explaining the importance and advantages of types, which for me is error prevention (specially in a collaborative work environment) and IDE integration (autocomplete, code hints, etc).

The book gets more advanced towards the later lessons. To the point that it became less useful to me. Tho I might revisit that section later as I get more experienced with TypeScript.

Some Highlights

I’m guilty of adding the type any whenever I get stuck. On the book, we’re exposed with the type unknown which is an interesting way of explicitly saying we don’t know what type this variable/parameter could be.

unknown should make you cautious: we have to provide a proper control flow to ensure type safety”

As in, testing the type of the variable before returning or making any operation.

When you have a rather complex data structure, an easy way of getting it as a type is using typeof.

“In TypeScript’s type system, the typeof operator takes any object and extracts the shape of it:” type Order = typeof defaultOrder

When learning TypeScript one thing that I could never find a proper explanation was when to use Type or Interface. I am still unsure, but I can see how one can have advantages over the other:

“Declaration merging for interfaces means we can declare an interface at separate positions in the same file, with different properties, and TypeScript combines all declarations and merges them into one.”

declare global {
  interface Window {
    isDevelopment: boolean


As you can see by my reviews I’m a huge fan of the Smashing Books, and I can honestly say that this is by far their best book. A joy to read and very insightful.

Grab a copy of the book.

J. Pedro Ribeiro

I’m a Brazilian front-end developer living in London. This website features some of my latest projects and my thoughts on anything web related.
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