title: how to get field type from store in Extjs4?
body: <p>i wont to get store field type in Extjs4</p>
  
  <p>this code is working under Extjs 3.3.2 </p>
  
  <pre><code>var f = store.fields.get(id); // store field name in parameter its return object
  alert(f.type.type); //its give me data type of that field 
  </code></pre>
  
  <p>but above code is not working in Extjs4 its give error get of undefine </p>
  
  <p>so how to know store field type </p>
  
  <p>my sore is </p>
  
  <pre><code>var data_sample = new Ext.data.SimpleStore({
      fields: [
          {name: 'yr', type: 'string'}
          ,{name: 'sales', type: 'int'}
          ,{name: 'expenses', type: 'int'}
      ],
      data: [['2004',1000,400],['2005',1170,460],['2006',860,580],['2007',1030,540]]
  });
  
  
  var year = store.data.get(0).get('yr'); 
  if ( year.constructor == (new Date).constructor){ 
  alert("date"); 
  }
  </code></pre>
  
  <p>this give me error in ie browser year is null</p>