Write Hello World in TypeScript

What is TypeScript?

“TypeScript is JavaScript for application-scale development.”

TypeScript is an open-source programming language. It is developed by Microsoft. It follows JavaScript syntactically but adds more features to it. It is a superset of JS.

Feature of TS

• Purely object-oriented, with features like classes, objects, and interfaces like Java
• TypeScript supports other JS libraries
• Any valid .js file can be renamed to .ts and compiled with other TypeScript files
• TypeScript is portable

Running a TS code

Browsers natively does not understand typescript, but they understand javascript. So in order to run typescript codes, first it is transpiled to javascript.
tsc : is a typescript compiler(transpiler) that converts typescript code into javascript.
You can install tsc by running following command:

npm install -g typescript

Write your first program

1. Create a file named "helloworld.ts".
2. Add these lines of code.

var greet: string = "Greetings"; 
var message: string = "MLH Local Hack Day!"; 
console.log(greet + " from " + message); 

1. To compile, run the following command: tsc helloworld.ts

This command will generate a javascript file with name helloworld.js

1. Run the javascript file using the following command on command line :

node helloworld.js

1. Output:

Greetings from MLH Local Hack Day!

Built With

• javascript
• typescript