check to see if item exists in store and insert it.

gistfile1.js

function processData(item, request){
      var value = myStore.getValue(item, 'group');
      var exist = myStore.getValue(item, value);
      var child = myStore.getValue(item, "name");
      console.debug(exist);
      if (undefined == exist){
        console.debug(exist + " Create " + value + " " + child);
        myStore.newItem({name: value, children:[{_reference: [child]}]});
        myStore.save;
      } 
}
var data = { identifier: 'name', label: 'name', items: [{ name:"Egypt", type:"country", group:"Africa" }]};
dojo.require('dojo.data.ItemFileWriteStore');
var myStore = new dojo.data.ItemFileWriteStore( { data: data });
myStore.fetch( { onItem: processData});

myStore.fetch( { onItem: function(item) { console.log( myStore.getValue( item, "name") ) } });