Headless browsers are a web browser without a graphical user interface that can be
controlled from a command line interface for the purpose of web page automation (e.g.,
functional testing, scraping, unit testing, etc.). Think of headless browsers as a browser that
you can run from the command line that can retrieve and traverse web pages.
The most common headless browsers are:
PhantomJS
slimerjs
trifleJS
basic usage：
