Gain insights into TypeScript's core concepts, from basics to advanced type checking and iterators. Learn about static typing and JS library support through practical, hands-on experience.

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If you’re looking to move beyond vanilla JavaScript and take your skills to the next level, then you’ve come to the right place. TypeScript is an in-demand language that sits on top of JavaScript. This means you can do everything you can in JavaScript with TypeScript, but also enjoy countless other perks including support for JS libraries, NPM, static typing, and much more.

In this course, you’ll start from the beginning and work your way up to more advanced concepts like type checking, iterators, and manipulating objects and arrays. You'll get a chance to get your hands dirty with plenty of real practice along the way.

For JavaScript developers, TypeScript is a must-know language, not only for today but also for years to come. Don't miss out.

Learn TypeScript: The Complete Course for Beginners

# Dangerous world
You must avoid (as much as possible) the type `any`, principally because it can hold any value and therefore doesn’t enforce any protections. If you are integrating an existing JavaScript project with TypeScript, every variable will be, by default, set to `any` until they are defined. 



let x: any = "string";
x = true;
x = { title: "Object with a string member" };
x = [1, 2, 3];
x = 1;

This is also the case with a value coming from an Ajax response in JSON format. Every `any` variable will let you assign any value but could also invoke any function.


The following code has a response of type `any` on **line 8**. Unfortunately, the response can be a string or a JSON object of any form. It is possible to mitigate this issue with *casting*, which you will see later to not propagate the `any` further in the code. 

> Move your cursor above `req.response` in the following code (line 8) to see the type of `any`.
 

In this lesson, you will learn about a variable type that you should only use in a particular situation.

Introduction

The Basics of Variables

Comment

Enum

Generic Type

Functions

Mapped Type

Objects

Index Signature

Variables Advanced

Exception

Alias

Type Checking

Iterators

Manipulating Objects and Array

Sharing Code

Conclusion

Avoiding `any` at Any Time Possible

Dangerous world #