ExtCombox読み込みJson設定デフォルトアクセス

ExtのComboxは言い方が違っていて、自分で実現したので、デブに伝言を残してください.
 
ファイルディレクトリ|--resource_type_combx.js   |--resource_type_combx.json
resource_type_combx.jsファイル
 

Ext.onReady(function(){
    // JSON
 var resourceTypeStore= new Ext.data.Store({
     proxy: new Ext.data.HttpProxy({
          url: "resource_type_combx.json"
     }),
     reader: new Ext.data.JsonReader({
     fields: [
            "resource_type_title","selected","resource_type_id"
        ]
      })
   });
   resourceTypeStore.load();
   //     
resourceTypeStore.on("load",function(ds,records,o){
     for(i=0;i<records.length;i++){
        if(records[i].data.selected=="yes"){
 combo.setValue(records[i].data.resource_type_title);
         }
      }
   });
   
    var combo = new Ext.form.ComboBox({
        name:"combox",
        fieldLabel: "    ", 
        hiddenName:"       name ", 
        store: resourceTypeStore,
        displayField:"resource_type_id",
        valueField:"resource_type_title",
        typeAhead: true,
        mode: "local",
        triggerAction: "all",
        emptyText:"Select a state...",
        selectOnFocus:true,
        applyTo: "local-states",
        valueNotFoundText:1,
        editable:false,
        //        
        listeners:{
          select: function(combo, record, index) {
          alert(combo.getValue());
         }
        }
    });
});

 resource_type_combx.jsonファイル

[
{"resource_type_title":"Extjs","resource_type_title":"1"},
{"resource_type_title":"Extjs1","resource_type_title":"2"},
{"resource_type_title":"extjs3","resource_type_title":"3","selected":"yes"}
]