a11y/audits.js

Runs an accessibility audit against a URL

/* eslint-env phantomjs, browser */
/* globals axs */
'use strict';

/**
 * Conducts audits using the Chrome Accessibility Tools and PhantomJS.
 */
var system = require('system');
var webpage = require('webpage').create();

var opts = JSON.parse(system.args[1]);
var PAGE_TIMEOUT = 9000;
var TOOLS_PATH = 'node_modules/accessibility-developer-tools/dist/js/axs_testing.js';
var BIND_POLYFILL_PATH = 'node_modules/phantomjs-polyfill/bind-polyfill.js';

function formatTrace(trace) {
    var src = trace.file || trace.sourceURL;
    var fn = (trace.function ? ' in function ' + trace.function : '');
    return '→ ' + src + ' on line ' + trace.line + fn;
}

// `console.error` is broken in PhantomJS
console.error = function () {
    system.stderr.writeLine([].slice.call(arguments).join(' '));
};

// Need to polyfill bind...
webpage.onInitialized = function () {
    webpage.injectJs(BIND_POLYFILL_PATH);
};

webpage.settings.resourceTimeout = PAGE_TIMEOUT;

webpage.viewportSize = {
    width: opts.width,
    height: opts.height
};

webpage.onResourceTimeout = function (err) {
    console.error('Error code:' + err.errorCode + ' ' + err.errorString + ' for ' + err.url);
    phantom.exit(1);
};

webpage.onError = opts.verbose ? function (err, trace) {
    console.error(err + '\n' + formatTrace(trace[0]) + '\n');
} : function () {
};

webpage.open(opts.url, function (status) {
    if (status === 'fail') {
        console.error('Couldn\'t load url: ' + JSON.stringify(opts.url));
        phantom.exit(1);
    }

    // Inject axs_testing
    webpage.injectJs(TOOLS_PATH);

    window.setTimeout(function () {
        var ret = webpage.evaluate(function () {
            var results = axs.Audit.run();

            var audit = results.map(function (result) {
                var DOMElements = result.elements;
                var message = '';

                if (DOMElements !== undefined) {
                    for (var i = 0; i < DOMElements.length; i++) {
                        var el = DOMElements[i];
                        message += '\n';
                        // Get query selector not browser independent. catch any errors and
                        // default to simple tagName.
                        try {
                            message += axs.utils.getQuerySelectorText(el);
                        } catch (err) {
                            message += ' tagName:' + el.tagName;
                            message += ' id:' + el.id;
                        }
                    }
                }

                return {
                    code: result.rule.code,
                    heading: result.rule.heading,
                    result: result.result,
                    severity: result.rule.severity,
                    url: result.rule.url,
                    elements: message
                };
            });

            return {
                audit: audit,
                report: axs.Audit.createReport(results)
            };
        });

        if (!ret) {
            console.error('Audit failed');
            phantom.exit(1);
            return;
        }

        console.log(JSON.stringify(ret));
        // Must do crazy song and dance to get phantom to exit properly
        // https://github.com/ariya/phantomjs/issues/12697
        webpage.close();
        setTimeout(function () {
            phantom.exit();
        }, 0);
    }, opts.delay * 1000);
});