How DOM element matches selectors

findMatchingSelectors.js

function findMatchingSelectors(dom) {
    var isMatch = isSelectorMatch.bind(null, dom);
    var result = [];

    if (dom.id) {
        var idSelectors = idSelectorMap[dom.id].filter(isMatch);
        result.push.apply(result, idSelectors);
    }

    dom.classList.forEach(function (className) {
        var classSelectors = classSelectorMap[className].filter(isMatch);
        result.push.apply(result, classSelectors);
    });

    var tagSelectors = tagSelectorMap[dom.nodeName].filter(isMatch);
    result.push.apply(result, tagSelectors);

    var remainingSelectors = remainingSelectorList.filter(isMatch);
    result.push.apply(result, remainingSelectors);

    return result;
}

function isSelectorMatch(dom, selector) {
    // ...
}