"kind"
          /
        "type"
    /     |     \
widget widget widget

var widgets = [...arrayOfWidgets];

var remove = function(widgetId) {
    widgets[widgetId].getChildWidgetIds().forEach(function(childWidgetId) {
        // `remove` is defined and accessible
        // at the time this is called
        remove(widgets[childWidgetId]);
    });

    delete widgets[$pageId];
};

remove(widgets[pageId]);

$widgets = [...arrayOfWidgets];

$remove = function($widgetId) use (&$widgets, &$remove) {
    foreach ($widgets[$widgetId]->getChildWidgetIds() as $childWidgetId) {
        $remove($widgets[$childWidgetId]);
    }

    unset($widgets[$widgetId]);
};

$remove($widgets[widgetId]);