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.. index:: selector, DOM, HTML

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>
.. index:: CSS, CSS3

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();
    });
});
.. index:: XPath

XPath

.. versionadded:: 0.6.8

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.