Thread by @akoskm

A Short Introduction to TypeScript 💙

🧵👇

TypeScript (TS) is a superset of JavaScript (JS) - meaning: any JS code you write is already valid TS code (not necessarily error-free though 😄).

The TypeScript compiler turns TypeScript into JavaScript.

So what's to point of all this if it's turned into JavaScript anyway? 🤔

The TypeScript compiler analyses your code. It creates itself a map describing how all your code is related - based mostly on the types you provide.

This is called Static type-checking.

If you look carefully at the code below you'll notice that it's 🤏 close to being 100% JS.

Yes, it's the extra "name: string" that does all this magic - and the TypeScript compiler of course.

This is of the Primitive TypeScript types, there are three in total:

🔹string
🔹number
🔹boolean

There's also an Array to combine all these and a special type called "any".

The TypeScript compiler is also smart enough to figure out things for itself.
It can detect types in your code based on the type of the initializer:

For example, in the above code, writing:

const firstName = 'Bob'

wouldn't result in an error but:

function log(message)

would

What does the above error message mean, why does TS generate it? What's any type anyway? 🤭

This is only the tip of the iceberg 🧗bear with me in the next two weeks and we'll explore all these concepts.

Everything you see here you can also try out in typescriptlang.org/play.

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Until next time 👋