Deep extend of JSON-type settings (JS objects) with options (JS objects)

updateSettings.js

/**
 * @param {object} settings
 * @param {object} options
 * @returns {object}
 */
function updateSettings(settings, options) {
    var updatedSettings = {};
    if (typeof settings !== 'undefined') {
        Object.assign(updatedSettings, settings);
    }
    Object
        .keys(options)
        .forEach(function(k) {
            // Avoid breaking objects, when some JSON encoders parse empty associative arrays as empty numeric arrays
            if (!(
                typeof updatedSettings[k] !== 'undefined' &&
                updatedSettings[k] !== null &&
                updatedSettings[k].constructor.name === 'Object' &&
                options[k].constructor.name === 'Array' &&
                options[k].length === 0
            )) {
                updatedSettings[k] = (options[k] !== null && options[k].constructor.name === 'Object' ?
                    updateSettings(updatedSettings[k], options[k]) :
                    options[k]
                );
            }
        });

    return updatedSettings;
}