Update operation in SharePoint 2010 REST API

updateListItem.js

function updateListItem(webUrl,listName,itemId,itemProperties,success, failure)
{
   getListItemById(webUrl,listName,itemId,function(item){
   
      $.ajax({
         type: 'POST',
         url: item.__metadata.uri,
         contentType: 'application/json',
         processData: false,
         headers: {
                "Accept": "application/json;odata=verbose",
                "X-HTTP-Method": "MERGE",
                "If-Match": item.__metadata.etag
         },
         data: Sys.Serialization.JavaScriptSerializer.serialize(itemProperties),
         success: function (data) {
                success(data);
         },
         error: function (data) {
                failure(data);
         }
      });
    
   },
   function(error){
       failure(error);
   });

}


//Usage: set Task Name & AssignedTo 
var taskProperties = {
    'TaskName': 'Approval',
    'AssignedToId': 12  
};

updateListItem('https://contoso.sharepoint.com/project/','Tasks',2,taskProperties,function(item){
    console.log('Task has been updated'); 
  },
  function(error){
    console.log(JSON.stringify(error));
  }
);