The showing event is triggered before the submenu is shown. showing is a useful event if you want to perform a function before the submenu is shown or if you want to block the submenu from showing by returning false.

$(function () {
    // Set showing event handler function
    $(".selector").wijmenu({
        showing : function (event, item) {
     
        }
    });
});

showing = function ( 
   event : any,
   item : any
) { };