Replaced .split("'").join("\\'") with .replace(/'/g, "\\'"). http://jsperf.com/split-join-vs-replace

underscore.js

@@ -629,7 +629,7 @@
     var c  = _.templateSettings;
     var tmpl = 'var __p=[],print=function(){__p.push.apply(__p,arguments);};' +
       'with(obj||{}){__p.push(\'' +
-      str.split("'").join("\\'")
+      str.replace(/'/g, "\\'")
          .replace(c.interpolate, function(match, code) {
            return "'," + code.replace(/\\'/g, "'") + ",'";
          })