Events & filters¶
CasperJS provides an event handler very similar to the nodejs‘ one; 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¶
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);
});
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.
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.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"
}
mouse.down¶
Arguments: args
Emitted when the mouse presses on something or somewhere with the left button.
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();
}
});
remote.callback¶
Arguments: data
Emitted when a remote window.callPhantom(data) 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 codeerrorString: error descriptionurl: resource urlid: resource id
run.complete¶
Arguments: None
Emitted when the whole series of steps in the stack have been executed.
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);
});
timeout¶
Arguments: None
Emitted when the execution time of the script has reached the Casper.options.timeout value.
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.
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.
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";
}
});
