Typing

The types on your Typescript makes your code safer. You have fewer Bugs and more Readable code because it clarifies your intentions. Types enables faster development and Navigation in your code. Hear are the Some of the basic types:

let isDone: boolean = false;
let height: number = 6;
let name: string = "bob";
let list: number[] = [1, 2, 3];
let list: Array = [1, 2, 3];
enum Color {Red, Green, Blue};
let c: Color = Color.Green;
let notSure: any = 4;
notSure = "maybe a string instead";
notSure = false;

We can notice let keyword used instead of var to declare a variable. This is because let allows you to declare variables to a limited scope of block or statement.

let is preferable because it reduces the scope in which an identifier is visible.

Babel's guide to ES6 says:

let is the new var.

Function Types

We have function types too

function add(x: number, y: number): number {
 return x + y;
}
let myAdd = function(x: number, y: number): number { return x+y; };

We can add types to each of the parameters and then to the function itself to add a return type.