loose instanceof: check constructor function name instead

src/types.js

@@ -26,7 +26,7 @@ module.exports = function enforce(type, value) {
     }
 
     default: {
-      if (value instanceof type) return
+      if (value.constructor.toString().match(/function (.*?)\(/)[1] === type.name) return
     }
   }
 

test/types.js

@@ -1,7 +1,7 @@
 var assert = require('assert')
 var enforceType = require('../src/types')
 
-function CustomType() {}
+function CustomType() { return "ensure non-greedy match".toUpperCase() }
 
 var types = ['Array', 'Boolean', 'Buffer', 'Number', 'String', CustomType]
 var values = [[], true, new Buffer(1), 1234, 'foobar', new CustomType()]