Creating if-else condition with ArcGIS API for JavaScript combo boxes?

I have an ArcGIS JavaScript API Web App that uses multiple combo boxes. I would like to create an if-else conditional statement between two fields in my feature layer. If one field is chosen in combo box one is 1 then combo box three should automatically populate to 3.

Below is my validate function for my request type.

 function changeonevent() {

  (dijit.byId("cbRequestType").on('change'), changeonevent (MFValue) {
    if (MFValue == 'Electronic Waste') {
   dijit.byID("cbMFSubType"). set ('value', 'Copy Machine'); 
   } else if MFValue == '...'{
   dijit.by.ID('cbMFSubType').set('value', 'Printer'); 
   }

Answer

Sorry for the concise comment, I can elaborate here. Say foo and bar are your combo box dijits:

dijit.byId('foo').on('change', function (new_value) {
  if (new_value == 'multi_family_refuse') {

    dijit.byId('bar').set('value', 'bar value 1');
  } else if (new_value == '...') {
    dijit.byId('bar').set('value', 'bar value 2');
  } else {
    ...
  }
});

if you have a lot of various states, try using switch statement instead.

Using your updated example:

  dijit.byId("cbRequestType").on('change', function (MFValue) {
    if (MFValue == 'Electronic Waste') {
      dijit.byID("cbMFSubType").set('value', 'Copy Machine'); 
    } else if MFValue == '...'{
      dijit.by.ID('cbMFSubType').set('value', 'Printer'); 
    }
  });