From d87b95bc1132f6f04595cbbf333dbba31f685be4 Mon Sep 17 00:00:00 2001
From: Rafael Weinstein <rafaelw@chromium.org>
Date: Thu, 22 Aug 2013 15:32:41 -0700
Subject: [PATCH] Cache expressions

R=arv
BUG=

Review URL: https://codereview.appspot.com/12815048
---
 src/polymer-expressions.js | 12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/src/polymer-expressions.js b/src/polymer-expressions.js
index d5a1df9..7489ef7 100644
--- a/src/polymer-expressions.js
+++ b/src/polymer-expressions.js
@@ -125,11 +125,17 @@
     return binding;
   }
 
+  // TODO(rafaelw): Implement simple LRU.
+  var expressionParseCache = {};
+
   function getExpressionBinding(model, expressionText) {
     try {
-      // TODO(rafaelw): Cache expressions.
-      var delegate = new ASTDelegate();
-      esprima.parse(expressionText, delegate);
+      var delegate = expressionParseCache[expressionText];
+      if (!delegate) {
+        delegate = new ASTDelegate();
+        esprima.parse(expressionText, delegate);
+        expressionParseCache[expressionText] = delegate;
+      }
 
       if (!delegate.expression && !delegate.labeledStatements.length)
         return;