Post on 27-Jan-2015
description
CasperJS
Howard 2013/12/22
CasperJS
CasperJS is an open source navigation scripting & testing utility written in Javascript for the PhantomJS WebKit headless browser and SlimerJS (Gecko).
It eases the process of defining a full navigation scenario and provides useful high-level functions, methods & syntactic sugar
Doing common tasks
such as: defining & ordering browsing navigation steps
filling & submitting forms
clicking & following links
capturing screenshots of a page (or part of it)
testing remote DOM
logging events
downloading resources, including binary ones
writing functional test suites, saving results as JUnit XML
scraping Web contents
Installation
Prerequisites PhantomJS
PhantomJS is a headless WebKit scriptable with a JavaScript API.
It has fast and native support for various web standards: DOM handling, CSS selector, JSON, Canvas, and SVG.
http://phantomjs.org/download.html
CasperJS
目標
列舉出目前 IPTECH TW 的目前可檢索的站台
A minimal scraping script
What did we just do? we created a new Casper instance
we started it and opened http://casperjs.org/
once the page has been loaded, we asked to print the title of that webpage (the content of its <title> tag)
then we opened another url, http://phantomjs.org/
once the new page has been loaded, we asked to print its title too
we executed the whole process
start(), then(), run(), exit()
start()
Signature: start(String url [, Function then])
Configures and starts Casper, then open the provided url and optionally adds the step provided by the then argument
then()
Signature: then(Function then)
run()
Signature: run(fn onComplete[, int time])
Runs the whole suite of steps and optionally executes a callback when they’ve all been done. Obviously, calling this method is mandatory in order to run the Casper navigation suite.
exit()
Signature: exit([int status])
Exits PhantomJS with an optional exit status code.
Note that the current Casper instance automatically binds the this keyword for you within step functions
start(), then(), run(), exit()
start(), then(), run(), exit()
?
casper module – fill
Signature: fill(String selector, Object values[, Boolean submit])
Fills the fields of a form with given values and optionally submits it. Fields are referenced by their name attribute.
click
click(Number x, Number y)
click(String selector)
Performs a click on the first element found matching the provided selector expression or at given coordinates if two numbers are passed
selector expression CSS3 selector strings
Xpath expressions
evaluate
Signature: evaluate(Function fn[, arg1[, arg2[, …]]])
Evaluates an expression in the current page DOM context
Understanding evaluate()
Think of the evaluate() method as a gate between the CasperJS environment and the one of the page you have opened;
Every time you pass a closure to evaluate(), you’re entering the page and execute code as if you were using the browser console.
waitForSelector
Signature: waitForSelector(String selector[, Function then, Function onTimeout, Number timeout])
Waits until an element matching the provided selector expression exists in remote DOM to process any next step
references
http://docs.casperjs.org/en/latest/quickstart.html
http://docs.casperjs.org/en/latest/modules/index.html
http://docs.casperjs.org/en/latest/modules/casper.html#start
http://docs.casperjs.org/en/latest/modules/casper.html#then
http://docs.casperjs.org/en/latest/modules/casper.html#run
http://docs.casperjs.org/en/latest/modules/casper.html#exit
http://docs.casperjs.org/en/latest/modules/casper.html#fill
http://docs.casperjs.org/en/latest/selectors.html
http://docs.casperjs.org/en/latest/modules/mouse.html#click