YellowLabTools/lib/tools/phantomas/custom_modules/modules/domHiddenYLT/domHiddenYLT.js

/**
 * Analyzes DOM hidden content
 */
/* global document: true, Node: true, window: true */

exports.version = '0.1.a';

exports.module = function(phantomas) {
    'use strict';

    // total length of HTML of hidden elements (i.e. display: none)
    phantomas.setMetric('hiddenContentSize'); // @desc the size of content of hidden elements on the page (with CSS display: none) @offenders

    // HTML size
    phantomas.on('report', function() {
        phantomas.evaluate(function() {
            (function(phantomas) {
                phantomas.spyEnabled(false, 'checking the hiddenContentSize');

                var runner = new phantomas.nodeRunner();

                runner.walk(document.body, function(node, depth) {
                    switch (node.nodeType) {
                        case Node.ELEMENT_NODE:
                            // @see https://developer.mozilla.org/en/DOM%3awindow.getComputedStyle
                            var styles = window.getComputedStyle(node);

                            if (styles && styles.getPropertyValue('display') === 'none') {
                                if (typeof node.innerHTML === 'string') {
                                    var size = node.innerHTML.length;
                                    phantomas.incrMetric('hiddenContentSize', size);

                                    // log hidden containers bigger than 1 kB
                                    if (size > 1024) {
                                        phantomas.addOffender('hiddenContentSize', phantomas.getDOMPath(node) + ' (' + size + ' characters)');
                                    }
                                }

                                // don't run for child nodes as they're hidden as well
                                return false;
                            }
                            break;
                    }
                });

                phantomas.spyEnabled(true);
            }(window.__phantomas));
        });
    });
};