.. _events_filters:

Events & filters
================

CasperJS provides an `event handler <#events>`_ very similar to the `nodejs <http://nodejs.org>`_' `one <https://github.com/joyent/node/blob/master/lib/events.js>`_; actually it borrows most of its codebase. CasperJS also adds `filters <#filters>`_, which are basically ways to alter values asynchronously.


.. index:: ! events

Events
------

Using events is pretty much straightforward if you're a node developer, or if you worked with any evented system before::

    var casper = require('casper').create();

    casper.on('resource.received', function(resource) {
        casper.echo(resource.url);
    });

Emitting you own events
+++++++++++++++++++++++

Of course you can emit your own events, using the ``Casper.emit()`` method::

    var casper = require('casper').create();

    // listening to a custom event
    casper.on('google.loaded', function() {
        this.echo('Google page title is ' + this.getTitle());
    });

    casper.start('http://google.com/', function() {
        // emitting a custom event
        this.emit('google.loaded');
    });

    casper.run();

Removing events
+++++++++++++++++++++++

You can also remove events. This is particularly useful when running a lot of tests where you might need to add and remove different events for different tests::

    var casper = require('casper').create();

    // listener function for requested resources
    var listener = function(resource, request) {
        this.echo(resource.url);
    };

    // listening to all resources requests
    casper.on("resource.requested", listener);

    // load the google homepage
    casper.start('http://google.com/', function() {
        this.echo(this.getTitle());
    });

    casper.run().then(function() {
        // remove the event listener
        this.removeListener("resource.requested", listener);
    });

Here is an example of how to use this in a casperjs test within the tearDown function.::

    var currentRequest;

    //Resource listener
    function onResourceRequested(requestData, request) {
        if (/\/jquery\.min\.js/.test(requestData.url)) {
            currentRequest = requestData;
        }
    }

    casper.test.begin('JQuery Test', 1, {
        setUp: function() {
            // Attach the resource listener
            casper.on('resource.requested', onResourceRequested);
        },

        tearDown: function() {
            // Remove the resource listener
            casper.removeListener('resource.requested', onResourceRequested);
            currentRequest = undefined;
        },

        test: function(test) {
            casper.start('http://casperjs.org/', function() {
                test.assert(currentRequest !== undefined, "JQuery Exists");
            });

            casper.run(function() {
                test.done();
            });
        }
    });

.. _events_list:

Events reference
++++++++++++++++

``back``
~~~~~~~~

**Arguments:** ``None``

Emitted when the embedded browser is asked to go back a step in its history.

``capture.saved``
~~~~~~~~~~~~~~~~~

**Arguments:** ``targetFile``

Emitted when a :index:`screenshot` image has been captured.

.. index:: click

``click``
~~~~~~~~~

**Arguments:** ``selector``

Emitted when the ``Casper.click()`` method has been called.

``complete.error``
~~~~~~~~~~~~~~~~~~

**Arguments:** ``error``

.. versionadded:: 1.1

Emitted when a complete callback has errored.

By default, CasperJS doesn't listen to this event, you have to declare your own listeners by hand::

    casper.on('complete.error', function(err) {
        this.die("Complete callback has failed: " + err);
    });

``die``
~~~~~~~

**Arguments:** ``message, status``

Emitted when the ``Casper.die()`` method has been called.

.. index:: download

``downloaded.file``
~~~~~~~~~~~~~~~~~~~

**Arguments:** ``targetPath``

Emitted when a file has been downloaded by :ref:`Casper.download() <casper_download>`; ``target`` will contain the path to the downloaded file.

.. index:: error

``error``
~~~~~~~~~

**Arguments:** ``msg, backtrace``

.. versionadded:: 0.6.9

Emitted when an error hasn't been explicitly caught within the CasperJS/PhantomJS environment. Do basically what PhantomJS' ``onError()`` native handler does.

.. index:: exit

``exit``
~~~~~~~~

**Arguments:** ``status``

Emitted when the ``Casper.exit()`` method has been called.

.. index:: fill

``fill``
~~~~~~~~

**Arguments:** ``selector, vals, submit``

Emitted when a form is filled using the ``Casper.fill()`` method.

``forward``
~~~~~~~~~~~

**Arguments:** ``None``

Emitted when the embedded browser is asked to go forward a step in its history.

.. index:: auth

``http.auth``
~~~~~~~~~~~~~

**Arguments:** ``username, password``

Emitted when http authentication parameters are set.

.. index:: HTTP

``http.status.[code]``
~~~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``resource``

Emitted when any given HTTP reponse is received with the status code specified by ``[code]``, eg.::

    casper.on('http.status.404', function(resource) {
        casper.echo(resource.url + ' is 404');
    })

``load.started``
~~~~~~~~~~~~~~~~

**Arguments:** ``None``

Emitted when PhantomJS' ``WebPage.onLoadStarted`` event callback is called.

``load.failed``
~~~~~~~~~~~~~~~

**Arguments:** ``Object``

Emitted when PhantomJS' ``WebPage.onLoadFinished`` event callback has been called and failed.

``load.finished``
~~~~~~~~~~~~~~~~~

**Arguments:** ``status``

Emitted when PhantomJS' ``WebPage.onLoadFinished`` event callback is called.

.. index:: log

``log``
~~~~~~~

**Arguments:** ``entry``

Emitted when the ``Casper.log()`` method has been called. The ``entry`` parameter is an Object like this::

    {
        level:   "debug",
        space:   "phantom",
        message: "A message",
        date:    "a javascript Date instance"
    }

.. index:: click

``mouse.click``
~~~~~~~~~~~~~~~

**Arguments:** ``args``

Emitted when the mouse left-click something or somewhere.

``mouse.down``
~~~~~~~~~~~~~~

**Arguments:** ``args``

Emitted when the mouse presses on something or somewhere with the left button.

``mouse.move``
~~~~~~~~~~~~~~

**Arguments:** ``args``

Emitted when the mouse moves onto something or somewhere.

``mouse.up``
~~~~~~~~~~~~

**Arguments:** ``args``

Emitted when the mouse releases the left button over something or somewhere.

``navigation.requested``
~~~~~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``url, navigationType, navigationLocked, isMainFrame``

.. versionadded:: 1.0

Emitted each time a navigation operation has been requested. Available navigation types are: ``LinkClicked``, ``FormSubmitted``, ``BackOrForward``, ``Reload``, ``FormResubmitted`` and ``Other``.

.. index:: HTTP

``open``
~~~~~~~~

``location, settings``

Emitted when an HTTP request is sent. First callback arg is the location, second one is a request settings Object of the form::

    {
        method: "post",
        data:   "foo=42&chuck=norris"
    }

``page.created``
~~~~~~~~~~~~~~~~

**Arguments:** ``page``

Emitted when PhantomJS' ``WebPage`` object used by CasperJS has been created.

``page.error``
~~~~~~~~~~~~~~

**Arguments:** ``message, trace``

Emitted when retrieved page leaves a Javascript error uncaught::

    casper.on("page.error", function(msg, trace) {
        this.echo("Error: " + msg, "ERROR");
    });

``page.initialized``
~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``WebPage``

Emitted when PhantomJS' ``WebPage`` object used by CasperJS has been initialized.

.. index:: HTTP

``page.resource.received``
~~~~~~~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``response``

Emitted when the HTTP response corresponding to current required url has been received.

.. index:: HTTP

``page.resource.requested``
~~~~~~~~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``request``

Emitted when a new HTTP request is performed to open the required url.

.. versionadded:: 1.1

**Arguments:** ``requestData, request``

You can also abort requests::

    casper.on('page.resource.requested', function(requestData, request) {
        if (requestData.url.indexOf('http://adserver.com') === 0) {
            request.abort();
        }
    });

``popup.created``
~~~~~~~~~~~~~~~~~

**Arguments:** ``WebPage``

Emitted when a new window has been opened.

``popup.loaded``
~~~~~~~~~~~~~~~~

**Arguments:** ``WebPage``

Emitted when a new window has been loaded.

``popup.closed``
~~~~~~~~~~~~~~~~

**Arguments:** ``WebPage``

Emitted when a new opened window has been closed.

``remote.alert``
~~~~~~~~~~~~~~~~

**Arguments:** ``message``

Emitted when a remote ``alert()`` call has been performed.

``remote.callback``
~~~~~~~~~~~~~~~~~~~

**Arguments:** ``data``

Emitted when a remote `window.callPhantom(data) <https://github.com/ariya/phantomjs/wiki/API-Reference-WebPage#wiki-webpage-onCallback>`_ call has been performed.

``remote.message``
~~~~~~~~~~~~~~~~~~

**Arguments:** ``msg``

Emitted when any remote console logging call has been performed.

``resource.error``
~~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``resourceError``

Emitted when any requested resource fails to load properly. The received ``resourceError`` object has the following properties:

- ``errorCode``: error code
- ``errorString``: error description
- ``url``: resource url
- ``id``: resource id

``resource.received``
~~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``resource``

Emitted when any resource has been received.

``resource.requested``
~~~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``request``

Emitted when any resource has been requested.

``run.complete``
~~~~~~~~~~~~~~~~

**Arguments:** ``None``

Emitted when the whole series of steps in the stack have been executed.

``run.start``
~~~~~~~~~~~~~

**Arguments:** ``None``

Emitted when ``Casper.run()`` is called.

``starting``
~~~~~~~~~~~~

**Arguments:** ``None``

Emitted when ``Casper.start()`` is called.

``started``
~~~~~~~~~~~

**Arguments:** ``None``

Emitted when Casper has been started using ``Casper.start()``.

``step.added``
~~~~~~~~~~~~~~

**Arguments:** ``step``

Emitted when a new navigation step has been added to the stack.

``step.complete``
~~~~~~~~~~~~~~~~~

**Arguments:** ``stepResult``

Emitted when a navigation step has been executed.

``step.created``
~~~~~~~~~~~~~~~~

**Arguments:** ``fn``

Emitted when a new navigation step has been created.

``step.error``
~~~~~~~~~~~~~~

**Arguments:** ``error``

.. versionadded:: 1.1

Emitted when a step function has errored.

By default, CasperJS doesn't listen to this event, you have to declare your own listeners by hand::

    casper.on('step.error', function(err) {
        this.die("Step has failed: " + err);
    });

``step.start``
~~~~~~~~~~~~~~

**Arguments:** ``step``

Emitted when a navigation step has been started.

``step.timeout``
~~~~~~~~~~~~~~~~

**Arguments:** ``[step, timeout]``

Emitted when a navigation step has timed out.

``timeout``
~~~~~~~~~~~

**Arguments:** ``None``

Emitted when the execution time of the script has reached the ``Casper.options.timeout`` value.

``url.changed``
~~~~~~~~~~~~~~~

**Arguments:** ``url``

.. versionadded:: 1.0

Emitted each time the current page url changes.

.. index:: viewport

``viewport.changed``
~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``[width, height]``

Emitted when the viewport has been changed.

``wait.done``
~~~~~~~~~~~~~

**Arguments:** ``None``

Emitted when a ``Casper.wait()``\ *operation ends.*

``wait.start``
~~~~~~~~~~~~~~

**Arguments:** ``None``

Emitted when a ``Casper.wait()`` operation starts.

``waitFor.timeout``
~~~~~~~~~~~~~~~~~~~

**Arguments:** ``[timeout, details]``

Emitted when the execution time of a ``Casper.wait*()`` operation has exceeded the value of ``timeout``.

``details`` is a property bag describing what was being waited on. For example, if ``waitForSelector`` timed out, ``details`` will have a ``selector`` string property that was the selector that did not show up in time.


.. index:: filters

Filters
-------

Filters allow you to alter some values asynchronously. Sounds obscure? Let's take a simple example and imagine you would like to alter every single url opened by CasperJS to append a ``foo=42`` query string parameter::

    var casper = require('casper').create();

    casper.setFilter('open.location', function(location) {
        return /\?+/.test(location) ? location += "&foo=42" : location += "?foo=42";
    });

There you have it, every single requested url will have this appended. Let me bet you'll find far more interesting use cases than my silly one ;)

Here'a the list of all available filters with their expected return value:

Filters reference
+++++++++++++++++

.. index:: screenshot

``capture.target_filename``
~~~~~~~~~~~~~~~~~~~~~~~~~~~

**Arguments:** ``args``

**Return type:** ``String``

Allows to alter the value of the filename where a screen capture should be stored.

``echo.message``
~~~~~~~~~~~~~~~~

**Arguments:** ``message``

**Return type:** ``String``

Allows to alter every message written onto stdout.

``log.message``
~~~~~~~~~~~~~~~

**Arguments:** ``message``

**Return type:** ``String``

Allows to alter every log message.

``open.location``
~~~~~~~~~~~~~~~~~

**Arguments:** ``args``

**Return type:** ``String``

Allows to alter every url before it being opened.

``page.confirm``
~~~~~~~~~~~~~~~~

**Arguments:** ``message``

**Return type:** ``Boolean``

.. versionadded:: 1.0

Allows to react on a javascript ``confirm()`` call::

    casper.setFilter("page.confirm", function(msg) {
        return msg === "Do you like vbscript?" ? false : true;
    });

``page.prompt``
~~~~~~~~~~~~~~~

**Arguments:** ``message, value``

**Return type:** ``String``

.. versionadded:: 1.0

Allows to react on a javascript ``prompt()`` call::

    casper.setFilter("page.prompt", function(msg, value) {
        if (msg === "What's your name?") {
            return "Chuck";
        }
    });
