select element in jquery, reading values

select.js

// selected index in select (dropdown)
$.fn.selectedIndex = function () {
	var index = 0;
	this.each(function () {
		index = +$(this).prop('selectedIndex');
		return false;
	});
	return index;
};

// selected value in select (dropdown)
$.fn.selectedValue = function () {
	var value = 0;
	this.each(function () {
		value = $(this).find("option:selected").val();
		return false;
	});
	return value;
};

// select all items in listbox
$.fn.selectAllItems = function () {
	this.each(function () {
		$(this).find('option').attr("selected", "selected");
	});
};