diff --git a/addons/base_graph/static/src/js/graph.js b/addons/base_graph/static/src/js/graph.js
index 0c0f9deb629..e1805f2d07a 100644
--- a/addons/base_graph/static/src/js/graph.js
+++ b/addons/base_graph/static/src/js/graph.js
@@ -84,8 +84,8 @@ openerp.base_graph.GraphView = openerp.base.Controller.extend({
         this.$element.html(QWeb.render("GraphView", {"fields_view": this.fields_view, "chart": this.chart,'view_id': this.view_id}));
         this.opration_fld = {};
         if (result.length){
-            for(res in result) {
-                for(fld in result[res]) {
+            for(var res in result) {
+                for(var fld in result[res]) {
                     if (typeof result[res][fld] == 'object') {
                         result[res][fld] = result[res][fld][result[res][fld].length - 1];
                     }
@@ -101,7 +101,7 @@ openerp.base_graph.GraphView = openerp.base.Controller.extend({
                 }
             }
 
-            for (i in result){
+            for (var i in result){
                 var gen_key = result[i][this.chart_info_fields]+"_"+result[i][this.group_field];
                 if (this.opration_fld[gen_key] == undefined){
                     var map_val = {}
@@ -182,7 +182,7 @@ openerp.base_graph.GraphView = openerp.base.Controller.extend({
             if (xystr[xystring] == undefined){
                 xyname = {};
                 xyname[self.chart_info_fields] = xystring;
-                for (j in self.group_list){
+                for (var j in self.group_list){
                     xyname[self.group_list[j]] = 0.0001;
                 }
                 xyname[newkey] = result[i][self.operator_field];
@@ -207,7 +207,7 @@ openerp.base_graph.GraphView = openerp.base.Controller.extend({
 
         //for legend color
         var grp_color = [];
-        for (i in self.group_list){
+        for (var i in self.group_list){
             var legend = {};
             if (self.group_list[i] == "val"){
                 legend['text'] = self.fields[self.operator_field]['string']
@@ -381,4 +381,4 @@ openerp.base_graph.GraphView = openerp.base.Controller.extend({
 
 };
 
-// vim:et fdc=0 fdl=0:
\ No newline at end of file
+// vim:et fdc=0 fdl=0:
diff --git a/doc/source/project.rst b/doc/source/project.rst
index faa15da2163..80ed0e86143 100644
--- a/doc/source/project.rst
+++ b/doc/source/project.rst
@@ -16,6 +16,43 @@ Source code repository
 Merge proposals
 +++++++++++++++
 
+Coding issues and coding conventions
+++++++++++++++++++++++++++++++++++++
+
+Javascript coding
+~~~~~~~~~~~~~~~~~
+
+Use ``var`` for *all* declarations
+**********************************
+
+In javascript (as opposed to Python), assigning to a variable which does not
+already exist and is not explicitly declared (via ``var``) will implicitly
+create a global variable. This is bad for a number of reasons:
+
+* It leaks information outside function scopes
+* It keeps memory of previous run, with potentially buggy behaviors
+* It may conflict with other functions with the same issue
+* It makes code harder to statically check (via e.g. IDE inspectors)
+
+.. note::
+    It is perfectly possible to use ``var`` in ``for`` loops:
+
+    .. code-block:: javascript
+
+        for (var i = 0; i < some_array.length; ++i) {
+            // code here
+        }
+
+    this is not an issue
+
+All local *and global* variables should be declared via ``var``.
+
+.. note:: generally speaking, you should not need globals in OpenERP Web: you
+          can just declare a variable local to your top-level function. This
+          way, if your widget/addon is instantiated several times on the same
+          page (because it's used in embedded mode) each instance will have its
+          own internal but global-to-its-objects data.
+
 Writing documentation
 +++++++++++++++++++++