javacript: indesign build library asset name string

gistfile1

function build_library_string(param_library_index) {
	// v.0.1.1 no library or asset return ""
	var library_index = param_library_index || 0 ;
	var my_library = app.libraries[library_index];
	var library_assets = my_library.assets;
	var str = "";

	if (app.libraries.length==0) {alert("There's no library."); return "";};
	if (library_assets.length==0) {alert("There's no asset in the library."); return "";};

	if (library_assets.length>0) {
		str = "::"; 	 // separation symbol
		for (var i = library_assets.length - 1; i >= 0; i--) {
			str += remove_file_extension(library_assets[i].name); // use can use asset with extension in library
			str += "::"; // separation symbol
		};		
	};
	return str;
};