From 5c58b52d40eb9aef0056a586505fbff51984682d Mon Sep 17 00:00:00 2001
From: Henry Zhu <hi@henryzoo.com>
Date: Tue, 1 Sep 2015 23:29:04 -0400
Subject: [PATCH] evaluation: evaluate typeof UnaryExpression

---
 packages/babel/src/traversal/path/evaluation.js | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/packages/babel/src/traversal/path/evaluation.js b/packages/babel/src/traversal/path/evaluation.js
index f4c1828c9d..a27e4e24e5 100644
--- a/packages/babel/src/traversal/path/evaluation.js
+++ b/packages/babel/src/traversal/path/evaluation.js
@@ -119,13 +119,20 @@ export function evaluate(): { confident: boolean; value: any } {
     }
 
     if (path.isUnaryExpression({ prefix: true })) {
-      var arg = evaluate(path.get("argument"));
+      var argument = path.get("argument");
+      var arg = evaluate(argument);
       switch (node.operator) {
         case "void": return undefined;
         case "!": return !arg;
         case "+": return +arg;
         case "-": return -arg;
         case "~": return ~arg;
+        case "typeof":
+          if (argument.isFunction()) {
+            return "function";
+          } else {
+            return typeof arg;
+          }
       }
     }