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