Cache isIntersection

js/id/core/node.js

@@ -23,6 +23,14 @@ _.extend(iD.Node.prototype, {
         return this.update({loc: loc});
     },
 
+    isIntersection: function(resolver) {
+        return resolver.transient(this, 'isIntersection', function() {
+            return resolver.parentWays(this).filter(function(parent) {
+                return parent.geometry(resolver) === 'line';
+            }).length > 1;
+        });
+    },
+
     asJXON: function(changeset_id) {
         var r = {
             node: {

js/id/svg/vertices.js

@@ -48,12 +48,6 @@ iD.svg.Vertices = function(projection, context) {
         return vertices;
     }
 
-    function isIntersection(entity, graph) {
-        return graph.parentWays(entity).filter(function (parent) {
-            return parent.geometry(graph) === 'line';
-        }).length > 1;
-    }
-
     function draw(groups, vertices, klass, graph, zoom) {
         groups = groups.data(vertices, function(entity) {
             return iD.Entity.key(entity) + ',' + zoom;
@@ -129,7 +123,7 @@ iD.svg.Vertices = function(projection, context) {
 
             if (entity.id in selected ||
                 entity.hasInterestingTags() ||
-                isIntersection(entity, graph)) {
+                entity.isIntersection(graph)) {
                 vertices.push(entity)
             }
         }