Learning TypeScript and NestJS

#typescript

In upcoming days I will shift my focus to learning NestJS and TypeScript for various reasons.

Javascript is a very popular language used by many small, big and huge companies (everywhere).
Has a huge community and a lot of resources.
Can be used for many things (Frontend, Backend, Mobile, Desktop, etc).
In performance wise, its very fast and efficient language (very good for high traffic applications, example: Twitter/X).
Its a must have skill/tool for any developer that wants to find a work in the tech industry.

So, I have enrolled in a course on Udemy to learn TypeScript and NestJS. I am on the first section of the course and here what I have learned so far:

Why does TypeScript exist?

Typescript is basically a superset of Javascript. It adds types to Javascript. It's like a layer on top of Javsacript. Typescript = Javascript + Type System.
Helps you catch errors before you run your code.
Helps you write better/Maintainable code.
Doesnt run in the browser or nodejs. It needs to be compiled to Javascript first.
It doesnt provide any performance benefits.
Its like a friend sitting next to you and telling you "Hey, you made a mistake here, you should fix it before you run your code".

What is a type?

A type is something that describes the different properties and functions that a value has. Lets take exmple of a string:

let color = 'red';

The type of color is string. It has properties like length and functions like toUpperCase().

Another example:

let count = 5;

The type of count is number. It has properties like toFixed() and functions like toString().

And there are 2 categories of types:

Primitive Types: (number, string, boolean, symbol, void, undefined, null)
They directly store/hold the value.
If you have variable a storing number 5, its like saying you have a number 5 in your hand.
Object Types: (functions, arrays, classes, objects).
They store a reference to the value.
They don't hold the actual data, but point to where the data is stored.
If you have a variable a storing an an object called Person, its like saying you have a piece of paper in your hand that has the address where the details about that Person are stored, not the Person itself.

Resources:

DEV Community