javascript - How can I stop an object method call before the ajax has completed -

i have following java script object

function eventtypeobj() {  alleventtypes = [];  // when object created go , event types can included in journey or clusters. $.ajax({         url: "/atomwebservice.svc/getdisplayeventtypes",         datatype: "json",         success: function(result) {             alleventtypes = eval("(" + result.d + ")");         }     });   // returns list of event type ids. this.geteventtypeids = function() {     var eventtypeids = [];     (var = 0; < alleventtypes.length; i++) {         eventtypeids.push(alleventtypes[i].id);     }     return eventtypeids; }; } 

i wondering if there way stop 1 calling eventtypeobj.geteventtypeids(); before ajax call in constructor has succeeded, , there no data in alleventtypes array?

something way better (im not guaranteeing 100% working, concept sound):

function eventtypeobj() {     this.alleventtypes = [];     this.hasloadedeventtypes = false;      var loadeventtypes = function(cb) {         $.ajax({             url: "/atomwebservice.svc/getdisplayeventtypes",             datatype: "json",             success: function(result) {                 this.alleventtypes = eval("(" + result.d + ")");                 this.hasloadedeventtypes = true;                 cb();             }         });     };       this.geteventtypeids = function(updateeventtypes, callback) {         var _geteventtypeids = function() {             var eventtypeids = [];             (var = 0; < this.alleventtypes.length; i++) {                 eventtypeids.push(this.alleventtypes[i].id);             }                 return eventtypeids;         };           if (!this.hasloadedeventtypes || updateeventtypes) {             loadeventtypes(function(){ callback(_geteventtypeids()); });         }         else callback(_geteventtypeids());     }; } 

example usage:

var eto = new eventtypeobj();  eto.geteventtypeids(false, function(eventtypeidarray) {    // stuff id array  });   /*     somewhere later on want updated eventtypeid array     in case event types have changed. */ eto.geteventtypeids(true, function(eventtypeidarray) {     // stuff updated ids });