When you set the checkable option to true and click on a menu item, the clicked item's state will be selected. A "ui-state-active" class will be added to the item so that the item behavior and the item appearance are different.
$(function () {
// Get value
var returnsValue; // Type: boolean
returnsValue = $(".selector").wijmenu("option", "checkable");
// Set value
var newValue; // Type: boolean
$(".selector").wijmenu("option", "checkable", newValue);
});