function initApp(el) {
	container = el;
	container.classList.add("extensions");
	container.content = $header;

	if (!$searchResult) {
		$searchResult = <ul className="list search-result scroll" />;
		container.append($searchResult);
	}

	if (!$explore) {
		$explore = collapsableList(strings.explore);
		$explore.ontoggle = loadExplore;
		$explore.$ul.onscroll = handleScroll;
		container.append($explore);
	}

	if (!$installed) {
		$installed = collapsableList(strings.installed);
		$installed.ontoggle = loadInstalled;
		//$installed.expand();
		container.append($installed);
	}

	Sidebar.on("show", onSelected);
}
Initialize extension app
@param {HTMLElement} el