Update List Items in SharePoint 2013 REST

SP2013.js

function updateJson(endpointUri,payload, success, error) 
{
    $.ajax({       
       url: endpointUri,   
       type: "POST",   
       data: JSON.stringify(payload),
       contentType: "application/json;odata=verbose",
       headers: { 
          "Accept": "application/json;odata=verbose",
          "X-RequestDigest" : $("#__REQUESTDIGEST").val(),
          "X-HTTP-Method": "MERGE",
           "If-Match": "*"
       },   
       success: success,
       error: error
    });
}

function getItemTypeForListName(name) {
    return"SP.Data." + name.charAt(0).toUpperCase() + name.slice(1) + "ListItem";
}

function updateListItem(webUrl,listTitle,listItemId,itemProperties,success,failure)
{
     var listItemUri =  webUrl + "/_api/web/lists/getbytitle('" + listTitle + "')/items(" + listItemId + ")";
     var itemPayload = {
       '__metadata': {'type': getItemTypeForListName(listTitle)}
     };
     for(var prop in itemProperties){
           itemPayload[prop] = itemProperties[prop];
     }
     updateJson(listItemUri,itemPayload,success,failure);
}

function deleteJson(endpointUri,success, error) {
  $.ajax({       
     url: endpointUri,   
     type: "POST",                
     contentType: "application/json;odata=verbose",
     headers: { 
        "Accept": "application/json;odata=verbose",
        "X-RequestDigest" : $("#__REQUESTDIGEST").val(),
        "X-HTTP-Method": "DELETE",
        "If-Match": "*"
     },   
     success: success,
     error: error
  });
}

function deleteListItem(webUrl,listTitle,listItemId,success,failure) {
  var listItemUri =  webUrl + "/_api/web/lists/getbytitle('" + listTitle + "')/items(" + listItemId + ")";

  deleteJson(listItemUri,success,failure);          
}

usage.js

var itemProperties = {'Title':'John Doe'};
updateListItem(_spPageContextInfo.webAbsoluteUrl,'Contacts',1,itemProperties,printInfo,logError);
deleteListItem(_spPageContextInfo.webAbsoluteUrl,'Contacts',1,printInfo,logError);
function printInfo()
{
    console.log('Item has been created');
}
function logError(error){
    console.log(JSON.stringify(error));
}