You need to use Proxy Type as 'jsonp'
createStore : function() {
var me = this;
me.createDataModel();
var store = Ext.create("Ext.data.Store", {
model : "tescoModel",
id : "tescoStore",
autoLoad : true,
remoteSort : true,
pageSize : 20,
proxy : {
type : "jsonp",
url : "http://www.techfortesco.com/groceryapi_b1/restservice.aspx",
limitParam : undefined,
startParam : undefined,
simpleSortMode : true,
pageParam : undefined,
noCache : false,
actionMethods : {
method : "POST"
},
reader : {
type : "json",
root : "Products",
totalProperty : "TotalProductCount"
}
}
});