From f5eb4b09157384c69f28e5cda38c620af8200c41 Mon Sep 17 00:00:00 2001
From: Brad Dunbar <dunbarb2@gmail.com>
Date: Wed, 14 Mar 2012 08:25:01 -0400
Subject: [PATCH] Clean up _.template.

* Cache regexes.
* Use object properties for lookup instead of switch.
---
 underscore.js | 59 ++++++++++++++++++++++++++++-----------------------
 1 file changed, 32 insertions(+), 27 deletions(-)

diff --git a/underscore.js b/underscore.js
index b956e21ce..4470eab44 100644
--- a/underscore.js
+++ b/underscore.js
@@ -902,19 +902,27 @@
   // guaranteed not to match.
   var noMatch = /.^/;
 
+  // Certain characters need to be escaped so that they can be put into a
+  // string literal.
+  var escapes = {
+    '\\': '\\',
+    "'": "'",
+    'r': '\r',
+    'n': '\n',
+    't': '\t',
+    'u2028': '\u2028',
+    'u2029': '\u2029'
+  };
+
+  for (var p in escapes) escapes[escapes[p]] = p;
+  var escaper = /\\|'|\r|\n|\t|\u2028|\u2029/g;
+  var unescaper = /\\(\\|'|r|n|t|u2028|u2029)/g;
+
   // Within an interpolation, evaluation, or escaping, remove HTML escaping
   // that had been previously added.
   var unescape = function(code) {
-    return code.replace(/\\(\\|'|r|n|t|u2028|u2029)/g, function(match, char) {
-      switch (char) {
-        case '\\': return '\\';
-        case "'": return "'";
-        case 'r': return '\r';
-        case 'n': return '\n';
-        case 't': return '\t';
-        case 'u2028': return '\u2028';
-        case 'u2029': return '\u2029';
-      }
+    return code.replace(unescaper, function(match, escape) {
+      return escapes[escape];
     });
   };
 
@@ -925,23 +933,20 @@
     var c  = _.templateSettings;
     var tmpl = 'var __p=[],print=function(){__p.push.apply(__p,arguments);};' +
       'with(obj||{}){__p.push(\'' +
-      str.replace(/\\/g, '\\\\')
-         .replace(/'/g, "\\'")
-         .replace(/\r/g, '\\r')
-         .replace(/\n/g, '\\n')
-         .replace(/\t/g, '\\t')
-         .replace(/\u2028/g, '\\u2028')
-         .replace(/\u2029/g, '\\u2029')
-         .replace(c.escape || noMatch, function(match, code) {
-           return "',_.escape(" + unescape(code) + "),\n'";
-         })
-         .replace(c.interpolate || noMatch, function(match, code) {
-           return "'," + unescape(code) + ",\n'";
-         })
-         .replace(c.evaluate || noMatch, function(match, code) {
-           return "');" + unescape(code) + ";\n__p.push('";
-         })
-         + "');}return __p.join('');";
+      str
+        .replace(escaper, function(match) {
+          return '\\' + escapes[match];
+        })
+        .replace(c.escape || noMatch, function(match, code) {
+          return "',_.escape(" + unescape(code) + "),\n'";
+        })
+        .replace(c.interpolate || noMatch, function(match, code) {
+          return "'," + unescape(code) + ",\n'";
+        })
+        .replace(c.evaluate || noMatch, function(match, code) {
+          return "');" + unescape(code) + ";\n__p.push('";
+        })
+        + "');}return __p.join('');";
     var func = new Function('obj', '_', tmpl);
     if (data) return func(data, _);
     return function(data) {