move isPromise into util folder

index.js

@@ -19,6 +19,7 @@ var mixin = require('utils-merge')
 var parseUrl = require('parseurl')
 var Route = require('./lib/route')
 var setPrototypeOf = require('setprototypeof')
+var isPromise = require('./lib/util/isPromise')
 
 /**
  * Module variables.
@@ -730,9 +731,3 @@ function wrap (old, fn) {
     fn.apply(this, args)
   }
 }
-
-function isPromise (val) {
-  return val &&
-    typeof val === 'object' &&
-    typeof val.then === 'function'
-}

lib/layer.js

@@ -13,6 +13,7 @@
  */
 
 var pathRegexp = require('path-to-regexp')
+var isPromise = require('./util/isPromise')
 
 /**
  * Module variables.
@@ -187,20 +188,6 @@ function decodeParam (val) {
   }
 }
 
-/**
- * Returns true if the val is a Promise.
- *
- * @param {*} val
- * @return {boolean}
- * @private
- */
-
-function isPromise (val) {
-  return val &&
-    typeof val === 'object' &&
-    typeof val.then === 'function'
-}
-
 /**
  * Loosens the given path for path-to-regexp matching.
  */

lib/util/isPromise.js

@@ -0,0 +1,15 @@
+/**
+ * Returns true if the val is a Promise.
+ *
+ * @param {*} val
+ * @return {boolean}
+ * @private
+ */
+
+function isPromise (val) {
+  return val &&
+    typeof val === 'object' &&
+    typeof val.then === 'function'
+}
+
+module.exports = isPromise