Events & filters

CasperJS provides an event handler very similar to the nodejsone; actually it borrows most of its codebase. CasperJS also adds filters, which are basically ways to alter values asynchronously.

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();

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 screenshot image has been captured.

click

Arguments: selector

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

complete.error

Arguments: error

New in version 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.

downloaded.file

Arguments: targetPath

Emitted when a file has been downloaded by Casper.download(); target will contain the path to the downloaded file.

error

Arguments: msg, backtrace

New in version 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.

exit

Arguments: status

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

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.

http.auth

Arguments: username, password

Emitted when http authentication parameters are set.

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.

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.

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.

page.resource.received

Arguments: response

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

page.resource.requested

Arguments: request

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

New in version 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.

remote.alert

Arguments: message

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

remote.callback

Arguments: data

Emitted when a remote window.callPhantom(data) 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

New in version 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

New in version 1.0.

Emitted each time the current page url changes.

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.

deatils 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.

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

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

New in version 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

New in version 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";
    }
});

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