Book Image

Test-Driven JavaScript Development

By : Ravi Kumar Gupta
Book Image

Test-Driven JavaScript Development

By: Ravi Kumar Gupta

Overview of this book

Initially, all processing used to happen on the server-side and simple output was the response to web browsers. Nowadays, there are so many JavaScript frameworks and libraries created that help readers to create charts, animations, simulations, and so on. By the time a project finishes or reaches a stable state, so much JavaScript code has already been written that changing and maintaining it further is tedious. Here comes the importance of automated testing and more specifically, developing all that code in a test-driven environment. Test-driven development is a methodology that makes testing the central part of the design process – before writing code developers decide upon the conditions that code must meet to pass a test. The end goal is to help the readers understand the importance and process of using TDD as a part of development. This book starts with the details about test-driven development, its importance, need, and benefits. Later the book introduces popular tools and frameworks like YUI, Karma, QUnit, DalekJS, JsUnit and goes on to utilize Jasmine, Mocha, Karma for advanced concepts like feature detection, server-side testing, and patterns. We are going to understand, write, and run tests, and further debug our programs. The book concludes with best practices in JavaScript testing. By the end of the book, the readers will know why they should test, how to do it most efficiently, and will have a number of versatile tests (and methods for devising new tests) to get to work immediately.
Table of Contents (16 chapters)
Test-Driven JavaScript Development
Credits
About the Authors
About the Reviewers
www.PacktPub.com
Preface
Index

Observer pattern using jQuery.Callbacks


Let's see an example of the observer pattern using the jQuery.Callbacks function.

To start with, let's add two functions which can help to understand the following flags that can be used with jQuery.Callbacks:

function newsAlert(notification) {
  alert(notification);
}
 

function appAlert(notification) {
  alert( "In appAlert function: "+notification);
  return false;
}

Possible flags available for jQuery.callbacks are listed as follows:

  • once: It will make sure that callback is called only once.

        var messages = $.Callbacks( "once" );
        messages.add(newsAlert);
        messages.fire("First Notificaiton");
        messages.add(appAlert);
        messages.fire("Second Notification");

    Here, the output is First Notification.

    Whenever run for the first time, we will get First Alert as an output.

  • memory: This flag will be used to keep track of old values and will call any of callback from the list that has been fired with the recent values:

        var messages = $.Callbacks...