# 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 testing framework:

    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

New in version 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 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.