selectTagsTwine.js

/*
LOAD THIS SCRIPT AFTER THE MAIN TWINE ENGINE
*/
function keySelectOption(inputs) {
    for (var i=0; i<inputs.length; i++) {
        document.onkeydown = function(e) {
        var option = document.activeElement;
            if (e.keyCode==40) {
                var node = option.nextSibling;
                while (node) {
                    if (node.tagName=='A') {
                        node.focus();
                        break;
                    }
                    node = node.nextSibling;
                }
            }
            else if (e.keyCode==38) {
                var node = option.previousSibling;
                while (node) {
                    if (node.tagName=='A') {
                        node.focus();
                        break;
                    }
                    node = node.previousSibling;
                }
            }
        };
    };
}
keySelectOption(document.getElementsByTagName('a'));
document.getElementsByTagName('a')[0].focus();