Introduction

REPL.it link:

https://repl.it/join/xbrnbjwx-jialinwu02

Basics

Typescript is a static type object-oriented programming language maintained by the Microsoft. It can be seen as a superset of Javascript. With the help of Typescript Compiler(TSC), we can convert typescript code to javascript and then it would be made understandable for the browser / node.

So, why do we need typescript if we can directly write in javascript? There are scenarios where javascript may not function that well.

Since typescript is a static type language, meaning that all the types can be checked during compile time, it can limit the number of mistakes during the run time. Thus easier to debug.
The static typing also provides highly productive development tools for JavaScript IDEs and practices, like static type checking.

As a result, typescript is gaining its popularity nowadays. It's crucial to understand typescript in a deeper level.

Syntax

Type

The biggest difference between JS and TS is the addition of static type checking.

function greeter(person) {
    return "Hello, " + person;
}

This is a normal javascript function. Let's see how should we rewrite it in typescript.

function greeter(person: string) {
    return "Hello, " + person;
}

If we try to put a different type as the person parameter, for example greeter([1,2,3]), we will get: