Book Image

Modern JavaScript Applications

By : Narayan Prusty
Book Image

Modern JavaScript Applications

By: Narayan Prusty

Overview of this book

Over the years, JavaScript has become vital to the development of a wide range of applications with different architectures. But JS moves lightning fast, and it’s easy to fall behind. Modern JavaScript Applications is designed to get you exploring the latest features of JavaScript and how they can be applied to develop high-quality applications with different architectures. Begin by creating a single page application that builds on the innovative MVC approach using AngularJS, then move forward to develop an enterprise-level application with the microservices architecture using Node to build web services. After that, shift your focus to network programming concepts as you build a real-time web application with websockets. Learn to build responsive, declarative UIs with React and Bootstrap, and see how the performance of web applications can be enhanced using Functional Reactive Programming (FRP). Along the way, explore how the power of JavaScript can be increased multi-fold with high performance techniques. By the end of the book, you’ll be a skilled JavaScript developer with a solid knowledge of the latest JavaScript techniques, tools, and architecture to build modern web apps.
Table of Contents (21 chapters)
Modern JavaScript Applications
Credits
About the Author
About the Reviewer
www.PacktPub.com
Preface
Index

Lazy evaluation


In programming, lazy evaluation is a strategy that delays the evaluation of values until they're needed. There are two means by which lazy evaluation is implemented by Bacon.js.

Type 1

A stream or property will not be attached to its data source until it has subscribers. Let's look at an example to understand this. Place this code in the index.js file:

var myButton_click_stream1 = $("#myButton").asEventStream("click").map(function(event){
  console.log(event);
  return event;
});

Here, when you click on the myButton button, nothing will be logged. Now, place this code in the index.js file:

myButton_click_stream1.onValue(function(event){})

Now when you click on the button, the event will be logged.

The log method is also considered as a subscriber.

Type 2

Methods such as map and combine* use lazy evaluation to avoid evaluating events and values that aren't actually needed. Lazy evaluation results in huge performance benefits in some cases.

But how do map and combine* know whether an...