add missing typeof, makes unit tests pass

gulpfile.js

@@ -101,7 +101,7 @@ const paths = {
 
 
 const tsBaseArgs = {
-  target: "es5",
+  target: "es6",
   jsx: "react",
   reactNamespace: "React",
   experimentalDecorators: true,

src/checkable.ts

@@ -216,7 +216,8 @@ export namespace Checkable {
           type: target,
         }, ["(root)"]);
         if (opts.validate) {
-          if (target.validate !== "function") {
+          if (typeof target.validate !== "function") {
+            console.error("target", target);
             throw Error("invalid Checkable annotion: validate method required");
           }
           // May throw exception

tsconfig.json

@@ -1,6 +1,6 @@
 {
   "compilerOptions": {
-    "target": "es5",
+    "target": "es6",
     "jsx": "react",
     "reactNamespace": "React",
     "experimentalDecorators": true,