From 3875af87636dd3e3a9e4e16ca132f1157e97b50e Mon Sep 17 00:00:00 2001
From: John Resig <jeresig@gmail.com>
Date: Thu, 30 Apr 2015 12:51:43 -0400
Subject: [PATCH] buildHTML's buildExpression is destructive, changing the tree
 object, this clones the object first before manipulating it.

---
 src/buildHTML.js | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/buildHTML.js b/src/buildHTML.js
index 94eead23c..c3cc4e970 100644
--- a/src/buildHTML.js
+++ b/src/buildHTML.js
@@ -1157,6 +1157,10 @@ var buildGroup = function(group, options, prev) {
  * nodes.
  */
 var buildHTML = function(tree, settings) {
+    // buildExpression is destructive, so we need to make a clone
+    // of the incoming tree so that it isn't accidentally changed
+    tree = JSON.parse(JSON.stringify(tree));
+
     var startStyle = Style.TEXT;
     if (settings.displayMode) {
         startStyle = Style.DISPLAY;