Iterate an ExtJS store, add result to Ajax request

How it is done

var Grid = this.getMyGridGrid(); // your grid
var Store = Grid.getStore();     // your grid's store    
var selected = Store.getRange();  // getRange = select all records

var Excerpt = []; // start with empty array
Ext.each(selected, function(item) {
    // add the fields that you want to include
    var Obj = {
        first_field: item.get('first_field'),  
        second_field: item.get('second_field'),
        third_field: item.get('third_field')
    };
    Excerpt.push(Obj); // push this to the array
}, this);

Ext.Ajax.request({
   url: 'server/execute_this_url',  // your url
   method: 'POST',
   params: {
      groups: Ext.encode(Excerpt),  // include the array in the params
   },
   success: function(result, action) {
      // decode the result and do something with it...
      var jsonData = Ext.decode(result.responseText);

      // do something with returned records 
      var jsonRecords = jsonData.records;
      Ext.iterate(jsonRecords, function(item) {
          var rec = Store.findExact('some_key', item.some_key);
          if (rec > -1) {
             Store.getAt(rec).set('field_found', true);
          }
      });
  }
});