Function getPreviousElement

docs/app/js/sanddance-app.js:24614–24644

(rootElement, currentElement, checkNode, suppressParentTraversal, traverseChildren, includeElementsInFocusZones, allowFocusRoot, tabbable)

    return false;
}
function getPreviousElement(rootElement, currentElement, checkNode, suppressParentTraversal, traverseChildren, includeElementsInFocusZones, allowFocusRoot, tabbable) {
    if (!currentElement || !allowFocusRoot && currentElement === rootElement) return null;
    var isCurrentElementVisible = isElementVisible(currentElement);
    // Check its children.
    if (traverseChildren && isCurrentElementVisible && (includeElementsInFocusZones || !(isElementFocusZone(currentElement) || isElementFocusSubZone(currentElement)))) {
        var childMatch = getPreviousElement(rootElement, currentElement.lastElementChild, true, true, true, includeElementsInFocusZones, allowFocusRoot, tabbable);
        if (childMatch) {
            if (tabbable && isElementTabbable(childMatch, true) || !tabbable) return childMatch;
            var childMatchSiblingMatch = getPreviousElement(rootElement, childMatch.previousElementSibling, true, true, true, includeElementsInFocusZones, allowFocusRoot, tabbable);
            if (childMatchSiblingMatch) return childMatchSiblingMatch;
            var childMatchParent = childMatch.parentElement;
            // At this point if we have not found any potential matches
            // start looking at the rest of the subtree under the currentParent.
            // NOTE: We do not want to recurse here because doing so could
            // cause elements to get skipped.
            while(childMatchParent && childMatchParent !== currentElement){
                var childMatchParentMatch = getPreviousElement(rootElement, childMatchParent.previousElementSibling, true, true, true, includeElementsInFocusZones, allowFocusRoot, tabbable);
                if (childMatchParentMatch) return childMatchParentMatch;
                childMatchParent = childMatchParent.parentElement;
            }
        }
    }
    // Check the current node, if it's not the first traversal.
    if (checkNode && isCurrentElementVisible && isElementTabbable(currentElement, tabbable)) return currentElement;
    // Check its previous sibling.
    var siblingMatch = getPreviousElement(rootElement, currentElement.previousElementSibling, true, true, true, includeElementsInFocusZones, allowFocusRoot, tabbable);
    if (siblingMatch) return siblingMatch;
    // Check its parent.
    if (!suppressParentTraversal) return getPreviousElement(rootElement, currentElement.parentElement, true, false, false, includeElementsInFocusZones, allowFocusRoot, tabbable);
    return null;
}
function getNextElement(rootElement, currentElement, checkNode, suppressParentTraversal, suppressChildTraversal, includeElementsInFocusZones, allowFocusRoot, tabbable) {
    if (!currentElement || currentElement === rootElement && suppressChildTraversal && !allowFocusRoot) return null;
    var isCurrentElementVisible = isElementVisible(currentElement);