Selectors
CasperJS makes a heavy use of selectors in order to work with the DOM, and can transparently use either CSS3 or XPath expressions.
All the examples below are based on this HTML code:
<!doctype html>
<html>
<head>
<meta charset="utf-8">
<title>My page</title>
</head>
<body>
<h1 class="page-title">Hello</h1>
<ul>
<li>one</li>
<li>two</li>
<li>three</li>
</ul>
<footer><p>©2012 myself</p></footer>
</body>
</html>
CSS3
By default, CasperJS accepts CSS3 selector strings to check for elements within the DOM.
To check if the <h1 class="page-title"> element exists in the example page, you can use:
var casper = require('casper').create();
casper.start('http://domain.tld/page.html', function() {
if (this.exists('h1.page-title')) {
this.echo('the heading exists');
}
});
casper.run();
Or if you're using the :doc:`testing framework <testing>`:
casper.test.begin('The heading exists', 1, function suite(test) {
casper.start('http://domain.tld/page.html', function() {
test.assertExists('h1.page-title');
}).run(function() {
test.done();
});
});
Some other convenient testing methods are relying on selectors:
casper.test.begin('Page content tests', 3, function suite(test) {
casper.start('http://domain.tld/page.html', function() {
test.assertExists('h1.page-title');
test.assertSelectorHasText('h1.page-title', 'Hello');
test.assertVisible('footer');
}).run(function() {
test.done();
});
});
XPath
You can alternatively use XPath expressions instead:
casper.start('http://domain.tld/page.html', function() {
this.test.assertExists({
type: 'xpath',
path: '//*[@class="plop"]'
}, 'the element exists');
});
To ease the use and reading of XPath expressions, a selectXPath helper is available from the casper module:
var x = require('casper').selectXPath;
casper.start('http://domain.tld/page.html', function() {
this.test.assertExists(x('//*[@id="plop"]'), 'the element exists');
});
Warning
The only limitation of XPath use in CasperJS is in the :ref:`casper.fill() <casper_fill>` method when you want to fill file fields; PhantomJS natively only allows the use of CSS3 selectors in its uploadFile method, hence this limitation.