Book Image

Getting Started with PhantomJS

By : Aries beltran
Book Image

Getting Started with PhantomJS

By: Aries beltran

Overview of this book

PhantomJS is a headless WebKit browser with JavaScript API that allows you to create new ways to automate web testing. PhantomJS is currently being used by a large number of users to help them integrate headless web testing into their development processes. It also gives you developers a new framework to create web-based applications, from simple web manipulation to performance measurement and monitoring.A step step-by by-step guide that will help you develop new tools for solving web and testing problems in an effective and quick way. The book will teach you how to use and maximize PhantomJS to develop new tools for web scrapping, web performance measurement and monitoring, and headless web testing. This book will help you understand PhantomJS’ scripting API capabilities and strengths.This book starts by looking at PhantomJS’ JavaScript API, features, and basic execution of scripts. Throughout the book, you will learn details to help you write scripts to manipulate web documents and fully create a web scrapping tool.Through its practical approach, this book strives to teach you by example, where each chapter focuses on the common and practical usage of PhantomJS, and how to extract meaningful information from the web and other services.By the end of the book, you will have acquired the skills to enable you to use PhantomJS for web testing, as well as learning the basics of Jasmine, and how it can be used with PhantomJS.
Table of Contents (13 chapters)
12
Index

Handling PhantomJS errors

PhantomJS scripts are not compiled, so we do expect that both runtime- and syntax-related errors could be thrown during script execution. These types of errors can be handled using the phantom object's onError callback.

If PhantomJS encounters a syntax error in the script, it will call the function defined for this callback; if there is no function defined for this callback, it will perform the default implementation and output the errors in the console as shown in the following screenshot:

Handling PhantomJS errors

PhantomJS will display the error message followed by a series of lines, which denotes the stack of the error call. It will also display the function or method with a source line number.

This information is also passed to any function that we've defined for the onError callback. The onError callback definition is as follows:

phantom.onError = function(msg, trace) {
  // code handling 
};

The onError callback will accept two parameters as shown in the preceding code. The...