PhantomJS - Overview
PhantomJS is said to be a headless browser because there is no involvement of browser while executing the JavaScript code. The execution will not be seen in the browser display, but on the command line prompt. The functionalities like CSS Handling, DOM Manipulation, JSON, Ajax, Canvas, SVG, etc., will all be taken care at the command prompt. PhantomJS does not have a GUI and hence, all its execution takes place at the command line.
Using PhantomJS, we can write to a file, read the contents of the file or upload a file, take an screen capture, convert the webpage into a pdf and lots more. With headless browsers, you get all the browser behavior i.e. Cookies, Http Request Methods i.e. GET /POST, Clearing Cookies, Deleting Cookies, etc., Reloading of Page, Navigating to a Different Page.
PhantomJS uses WebKit that has a similar browsing environment like the famous browsers – Google Chrome, Mozilla Firefox, Safari, etc. It also provides a lot of JavaScript API, which helps in taking screenshots, uploading of file, writing to file, reading a file, interacting with the web pages, etc.
PhantomJS does not support Flash or Video, as it requires plugins and it is difficult to support the same on the command line.
Features of PhantomJS
Let us now understand the features that PhantomJS offers.
Page Automation
PhantomJS allows you to read the page contents with the help of its API. It can help to manipulate the DOM, use external libraries to carry out the task required.
Screen Capture
PhantomJS helps in taking a screen capture of a page specified and save the same as an image in various formats like PNG, JPEG, PDF, and GIF. With the help of the screen capture, it can easily help to make sure the web content is fine.
PhantomJS offers properties and methods with the help of which it allows developers to adjust the size of the screenshots and specify the area they want to capture.
Headless Testing
PhantomJS helps testing of UI at the command line. While, with the help of a screenshot, it can easily help to find errors in the UI. PhantomJS sometimes cannot help with testing alone. However, it can be wrapped along with other testing libraries like Mocha, Yoeman, etc. You can take the help of PhantomJS to upload a file and submit the form.
PhantomJS can be used to test logins across the sites and make sure the security is not compromised. PhantomJS can be used along with other tools like CasperJS, Mocha, Qunit to make the testing more powerful.
Network Monitoring
One of the important features of PhantomJS is its usage to monitor the network connection using the API available. PhantomJS permits the inspection of network traffic; it is suitable to build various analysis on the network behavior and performance.
PhantomJS can be used to collect the data about the performance of the webpage in a live environment. PhantomJS can be used with tools like Yslow to gather performance metrics of any websites.
