From 1eccf093ac110813948e1f21fcad98dfe6eaf480 Mon Sep 17 00:00:00 2001
From: Martin Fischer <Arthur.Spooner@gmail.com>
Date: Sat, 7 Nov 2015 22:08:00 +0100
Subject: [PATCH 1/2] cloning old data before updating to fix #1378

---
 lib/DataSet.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/lib/DataSet.js b/lib/DataSet.js
index b87ddcd7..1ffadc93 100644
--- a/lib/DataSet.js
+++ b/lib/DataSet.js
@@ -243,10 +243,11 @@ DataSet.prototype.update = function (data, senderId) {
   var addOrUpdate = function (item) {
     var id = item[fieldId];
     if (me._data[id]) {
+      var oldData = util.extend({}, me._data[id]);
       // update item
       id = me._updateItem(item);
       updatedIds.push(id);
-      updatedData.push(item);
+      updatedData.push(oldData);
     }
     else {
       // add new item
@@ -513,7 +514,7 @@ DataSet.prototype.forEach = function (callback, options) {
   var filter = options && options.filter,
       type = options && options.type || this._options.type,
       data = this._data,
-      itemIds = Object.key(data),
+      itemIds = Object.keys(data),
       i,
       len,
       item,

From a09df56a45df8e9f4e2e1ca9dafa82ba23d82f0b Mon Sep 17 00:00:00 2001
From: Martin Fischer <Arthur.Spooner@gmail.com>
Date: Tue, 10 Nov 2015 20:10:12 +0100
Subject: [PATCH 2/2] defined a read only property 'data' to avoid breaking the
 api

---
 lib/DataSet.js | 10 +++++++++-
 1 file changed, 9 insertions(+), 1 deletion(-)

diff --git a/lib/DataSet.js b/lib/DataSet.js
index 1ffadc93..25ede879 100644
--- a/lib/DataSet.js
+++ b/lib/DataSet.js
@@ -274,7 +274,15 @@ DataSet.prototype.update = function (data, senderId) {
     this._trigger('add', {items: addedIds}, senderId);
   }
   if (updatedIds.length) {
-    this._trigger('update', {items: updatedIds, data: updatedData}, senderId);
+	var props = { items: updatedIds, oldData: updatedData };
+	// TODO: remove deprecated property 'data' some day
+	Object.defineProperty(props, 'data', {
+	  'get': (function() {
+	    console.warn('Property data is deprecated. Use DataSet.get(ids) to retrieve the new data, use the oldData property on this object to get the old data');
+	    return this.get(updatedIds);
+	  }).bind(this)
+	});
+    this._trigger('update', props, senderId);
   }
 
   return addedIds.concat(updatedIds);