Book Image

JavaScript JSON Cookbook

By : Ray Rischpater, Brian Ritchie, Ray Rischpater
Book Image

JavaScript JSON Cookbook

By: Ray Rischpater, Brian Ritchie, Ray Rischpater

Overview of this book

Table of Contents (17 chapters)
JavaScript JSON Cookbook
Credits
About the Author
About the Reviewers
www.PacktPub.com
Preface
Index

How to annotate simple types using TypeScript


Type annotations with TypeScript are simple decorators appended to the variable or function after a colon. There's support for the same primitive types as in JavaScript, and to declare interfaces and classes, which we will discuss next.

How to do it…

Here's a simple example of some variable declarations and two function declarations:

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

function circumference(radius: number) : number {
  var pi: number = 3.141592654;
  return 2 * pi * radius;
}

var user: string = "Ray";

console.log(greeter(user));
console.log("You need " + 
circumference(2) + 
  " meters of fence for your dog.");

This example shows how to annotate functions and variables.

How it works…

Variables—either standalone or as arguments to a function—are decorated using a colon and then the type. For example, the first function, greeter, takes a single argument, person, which must be a string. The second function, circumference...