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README.md

Casper.js

Casper.js is a navigation utility for PhantomJS. It eases the process of defining a full navigation scenario and provides useful high-level function, methods & syntaxic sugar for doing common tasks such as:

  • defining & ordering navigation steps
  • capturing screenshots of a page (or an area)
  • making assertions on remote DOM
  • logging events
  • evaluating dynamic code within the remote page environment
  • retrieve base64 encoded version of remote resources
  • catch errors and react accordingly

Quickstart

In the following example, we'll query google for two terms consecutively, capser and homer, and aggregate the result links in a standard Array. Running the script will output a standard JSON string containing both the logs and the results:

phantom.injectJs('path/to/casper.js');

// User defined functions
function q() {
    document.querySelector('input[name="q"]').setAttribute('value', '%term%');
    document.querySelector('form[name="f"]').submit();
}

function getLinks() {
    var links = document.querySelectorAll('h3.r a');
    return Array.prototype.map.call(links, function(e) {
        return e.getAttribute('href');
    });
}

// Casper suite
var links = [];
var casper = new phantom.Casper({
    logLevel: "info"
});
casper.start('http://google.fr/')
    .thenEvaluate(q, {
        term: 'casper'
    })
    .then(function(self) {
        links = self.evaluate(getLinks);
    })
    .thenEvaluate(q, {
        term: 'homer'
    })
    .then(function(self) {
        links = links.concat(self.evaluate(getLinks));
    })
    .run(function(self) {
        self.echo(JSON.stringify({
            result: self.result,
            links: links
        }, null, '  '));
        self.exit();
    })
;

Hint: Method chaining is not mandatory but provided as an alternative way to structure your code.

Run it:

$ phantomjs example.js
{
  "result": {
    "log": [
      {
        "level": "info",
        "space": "phantom",
        "message": "Starting…",
        "date": "Mon Sep 05 2011 16:10:56 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Running suite: 4 steps",
        "date": "Mon Sep 05 2011 16:10:56 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Step 1/4: http://www.google.fr/ (HTTP 301)",
        "date": "Mon Sep 05 2011 16:10:57 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Step 1/4: done in 1259ms.",
        "date": "Mon Sep 05 2011 16:10:57 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Step 2/4: http://www.google.fr/search?sclient=psy&hl=fr&site=&source=hp&q=casper&pbx=1&oq=&aq=&aqi=&aql=&gs_sm=&gs_upl= (HTTP 301)",
        "date": "Mon Sep 05 2011 16:10:58 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Step 2/4: done in 2145ms.",
        "date": "Mon Sep 05 2011 16:10:58 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Step 3/4: http://www.google.fr/search?sclient=psy&hl=fr&site=&source=hp&q=casper&pbx=1&oq=&aq=&aqi=&aql=&gs_sm=&gs_upl= (HTTP 301)",
        "date": "Mon Sep 05 2011 16:10:58 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Step 3/4: done in 2390ms.",
        "date": "Mon Sep 05 2011 16:10:58 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Step 4/4: http://www.google.fr/search?sclient=psy&hl=fr&source=hp&q=homer&pbx=1&oq=&aq=&aqi=&aql=&gs_sm=&gs_upl= (HTTP 301)",
        "date": "Mon Sep 05 2011 16:10:59 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Step 4/4: done in 3077ms.",
        "date": "Mon Sep 05 2011 16:10:59 GMT+0200 (CEST)"
      },
      {
        "level": "info",
        "space": "phantom",
        "message": "Done 4 steps in 3077ms.",
        "date": "Mon Sep 05 2011 16:10:59 GMT+0200 (CEST)"
      }
    ],
    "status": "success",
    "time": 3077
  },
  "links": [
    "http://fr.wikipedia.org/wiki/Casper_le_gentil_fant%C3%B4me",
    "http://fr.wikipedia.org/wiki/Casper",
    "http://casperflights.com/",
    "http://www.allocine.fr/film/fichefilm_gen_cfilm=13018.html",
    "/search?q=casper&hl=fr&prmd=ivns&tbm=isch&tbo=u&source=univ&sa=X&ei=cdhkTurpFa364QTB5uGeCg&ved=0CFkQsAQ",
    "http://www.youtube.com/watch?v=Kuvo0QMiNEE",
    "http://www.youtube.com/watch?v=W7cW5YlHaeQ",
    "http://www.imdb.com/title/tt0112642/",
    "http://blog.caspie.net/",
    "http://www.casperwy.gov/",
    "http://www.lequipe.fr/Cyclisme/CyclismeFicheCoureur147.html",
    "http://homer-simpson-tv.blog4ever.com/",
    "http://fr.wikipedia.org/wiki/Homer_Simpson",
    "http://en.wikipedia.org/wiki/Homer",
    "/search?q=homer&hl=fr&prmd=ivnsb&tbm=isch&tbo=u&source=univ&sa=X&ei=cthkTr73Hefh4QSUmt3UCg&ved=0CEQQsAQ",
    "http://www.youtube.com/watch?v=Ajd08hgerRo",
    "http://www.koreus.com/video/homer-simpson-photo-39-ans.html",
    "http://www.nrel.gov/homer/",
    "http://www.luds.net/homer.php",
    "http://www.thesimpsons.com/bios/bios_family_homer.htm",
    "http://www.homeralaska.org/",
    "http://homeralaska.com/"
  ]
}

CoffeeScript

You can also write Casper scripts using the CoffeeScript syntax:

phantom.injectJs "path/to/casper.js"

q = ->
    document.querySelector('input[name="q"]').setAttribute "value", "%term%"
    document.querySelector('form[name="f"]').submit()

getLinks = ->
    links = document.querySelectorAll("h3.r a")
    Array::map.call links, (e) ->
        e.getAttribute "href"

links = []

casper = new phantom.Casper verbose: true, logLevel: "debug"
casper.start "http://google.fr/"
casper.thenEvaluate q, term: "casper"
casper.then -> links = casper.evaluate getLinks
casper.thenEvaluate q, term: "homer"
casper.then -> links = links.concat casper.evaluate getLinks
casper.run ->
    out =
        result: casper.result
        links:  links
    casper.echo JSON.stringify out, null, "    "
    casper.exit()

Casper.js API Documentation

Code is quite heavily documented using jsdoc, but below you'll find the whole API documentation with added sample code added.

Casper([Object options])

Casper constructor accepts a single options argument which is an object. Available options are:

Name              | Type     | Default | Description
——————————————————+——————————+—————————+————————————————————————————————————————————————————————————————————
clientScripts     | Array    | []      | A collection of script filepaths to include to every page loaded
logLevel          | String   | "error" | Logging level (see logLevels for available values)
onDie             | function | null    | A function to be called when Casper#die() is called
onPageInitialized | function | null    | A function to be called after WebPage instance has been initialized
page              | WebPage  | null    | An existing WebPage instance
pageSettings      | Object   | {}      | PhantomJS's WebPage settings object
verbose           | Boolean  | false   | Realtime output of log messages

Example:

phantom.injectJs('path/to/casper.js');

var casper = new phantom.Casper({
    clientScripts:  [
        'includes/jquery.js',
        'includes/underscore.js'
    ],
    logLevel: "info",
    pageSettings: {
        loadImages:  false,
        loadPlugins: false
    }
});

But no worry, usually you'll just need to instantiate Casper using new phantom.Casper().

Casper#base64encode(String url)

Encodes a resource using the base64 algorithm synchroneously using client-side XMLHttpRequest.

NOTE: we cannot use window.btoa() because it fails miserably in the version of WebKit shipping with PhantomJS.

Example: retrieving google logo image encoded in base64:

var base64logo = null;
casper.start('http://www.google.fr/', function(self) {
    base64logo = self.base64encode('http://www.google.fr/images/srpr/logo3w.png');
}).run(function(self) {
    self.echo(base64logo);
});

Casper#capture(String targetFilepath, Object clipRect)

Proxy method for PhantomJS' WebPage#render. Adds a clipRect parameter for automatically setting page clipRect setting values and sets it back once done.

Example:

casper.start('http://www.google.fr/', function(self) {
    self.capture('google.png', {
        top: 100,
        left: 100,
        width: 500,
        height: 400
    });
}).run();

Casper#debugHTML()

Logs the HTML code of the current page directly to the standard output, for debugging purpose.

Example:

casper.start('http://www.google.fr/', function(self) {
    self.debugHTML();
}).run();

Casper#debugPage()

Logs the textual contents of the current page directly to the standard output, for debugging purpose.

Example:

casper.start('http://www.google.fr/', function(self) {
    self.debugPage();
}).run();

Casper#die(String message[, int status])

Exits phantom with a logged error message and an optional exit status code.

Example:

casper.start('http://www.google.fr/', function(self) {
    self.die("Fail.", 1);
}).run();

Casper#echo(String message)

Prints something to stdout.

Example:

casper.start('http://www.google.fr/', function(self) {
    self.echo('Page title is: ' + self.evaluate(function() {
        return document.title;
    }));
}).run();

Casper#evaluate(function fn[, Object replacements])

Evaluates an expression in the page context, a bit like what PhantomJS' WebPage#evaluate does, but can also replace values by their placeholer names.

Example:

casper.evaluate(function() {
    document.querySelector('#username').setAttribute('value', '%username%');
    document.querySelector('#password').setAttribute('value', '%password%');
    document.querySelector('#submit').click();
}, {
    username: 'sheldon.cooper',
    password: 'b4z1ng4'
});

Casper#evaluateOrDie(function fn[, String message])

Evaluates an expression within the current page DOM and die() if it returns anything but true.

Example:

casper.start('http://foo.bar/home', function(self) {
    self.evaluateOrDie(function() {
        return /logged in/.match(document.title);
    }, 'not authenticated');
}).run();

Casper#exit([int status])

Exits PhantomJS with an optional exit status code.

Casper#log(String message[, String level, String space)

Logs a message with an optional level in an optional space. Available levels are debug, info, warning and error. A space is a kind of namespace you can set for filtering your logs. By default, Casper logs messages in two distinct spaces: phantom and remote, to distinguish what happens in the PhantomJS environment from the remote one.

Example:

casper.start('http://www.google.fr/', function(self) {
    self.log("I'm logging an error", "error");
}).run();

Casper#repeat(int times, function then)

Repeats a navigation step a given number of times.

Example:

var i = 0;
casper.start('http://foo.bar/home', function(self) {
    self.evaluateOrDie(function() {
        return /logged in/.match(document.title);
    }, 'not authenticated');
}).repeat(5, function(self) {
    self.echo("I am step #" + ++i);
}).run();

Casper#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.

Casper suite won't run:

casper.start('http://foo.bar/home', function(self) {
    // ...
}).then(function(self) {
    // ...
});

Casper suite will run:

casper.start('http://foo.bar/home', function(self) {
    // ...
}).then(function(self) {
    // ...
}).run();

Casper#start(String url[, function then])

Configures and starts Casper, then open the provided url and optionnaly adds the step provided by the then argument.

Example:

casper.start('http://google.fr/', function(self) {
    self.echo("I'm loaded.");
}).run();

Alternatively:

casper.start('http://google.fr/');
casper.then(function(self) {
    self.echo("I'm loaded.");
});
casper.run();

Please note that you must call the start() method in order to be able to add navigation steps and run the suite. If you don't you'll get an error message inviting you to do so anyway.

Casper#then(function fn)

The standard way to add a new navigation step to the Casper suite by provide a callback function which will be executed when the requested page is loaded.

Example:

casper.start('http://google.fr/').then(function(self) {
    self.echo("I'm in your google.");
}).run();

Please note that usage of the self argument is not mandatory, it's just pythonic-like syntaxic sugar. You can perfectly use this alternative:

casper.start('http://google.fr/').then(function() {
    casper.echo("I'm in your google.");
}).run();

If you want to open a page as a next step in your navigation scenario, please refer to the Casper#thenOpen() method documentation.

Casper#thenEvaluate(function fn[, Object replacements])

Adds a new navigation step to perform code evaluation within the current retrieved page DOM.

Example:

// Querying for "Chuck Norris" on Google
casper.start('http://google.fr/').thenEvaluate(function() {
    document.querySelector('input[name="q"]').setAttribute('value', '%term%');
    document.querySelector('form[name="f"]').submit();
}, {
    term: 'Chuck Norris'
}).run();

Casper#thenOpen(String location[, function then])

Adds a new navigation step for opening a new location, and optionnaly add a next step when its loaded.

Example:

casper.start('http://google.fr/').then(function(self) {
    self.echo("I'm in your google.");
}).thenOpen('http://yahoo.fr/', function(self) {
    self.echo("Now I'm in your yahoo.")
}).run();

Casper#thenOpenAndEvaluate(String location[, function then, Object replacements])

Basically a shortcut for opening an url and evaluate code against remote DOM environment.

Example:

casper.start('http://google.fr/').then(function(self) {
    self.echo("I'm in your google.");
}).thenOpenAndEvaluate('http://yahoo.fr/', function() {
    document.querySelector['form'].submit();
}).run();

Licensing

Casper.js is released under the terms of the MIT license.

Now what

Feel free to play with the code and report an issue on github. I'm also reachable on twitter.