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

# What is the mapped type?
The mapped type allows for creating a new type from an existing one. Using the term *map* refers to pointing existing members to a new type by a custom logic that is unique to the mapper implementation. 

A good example is to have an existing interface keep all the same members, but make them *optional* or *read-only*. 

## Advantages of the mapped type
### First advantage
The mapped type has two advantages over the previous versions of TypeScript that didn’t support it. 

Before the mapped type, we needed to create an additional interface to reflect the desired final state. This extra step pollutes the codebase of several interfaces, depending on how you transform the interface and how many duplicates for each different interface need to be mapped. 

Furthermore, for each original interface, you need to synchronize every other one each time the interface changes. It rapidly becomes hard to maintain. 

The following code demonstrates how we needed two interfaces to have one read-only and another without a mapped type. This was prior to the introduction of a mapped type in the language. The code is trying to have two objects with the same attributes, one that can alter its values once initialized and another that should block any future assignments.


In this lesson, we will set the groundwork for the upcoming lessons on the mapped type.


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

Definition and Usages

What is the mapped type?