Writing JavaScript code with static types

The first thing that you'll notice when working with TypeScript are its static types, in addition to all of the JavaScript types, indicated on the following table:

   
Primitives           
Objects

      
String           
Function

      
Number           
Array

      
Null           
Prototypes

      
Undefined           


      
Boolean           


      
Symbol           

  

This means that you can declare the types of variables; it's pretty simple to assign a type to a variable. Let's look at some examples, using JavaScript types only:

function Myband () {
  let band: string;
  let active: boolean;
  let numberOfAlbuns: number;
}

With TypeScript, we have a few more types, as we'll see in the following sections.