Add support for functions in router

Can add a function as to match a route. The function takes in a string
url segment and returns some value if the route matches or returns null
or undefined for no match.

Example usage:

function toInt(part) {
  var results = /^(\d+)$/.exec(part)
  return results ? parseInt(results[0], 10) : null
}

var router = new Router()
router.add(['/by/order', toInt], function (val) {
  // val === 123
})

router.route('/by/order/123')

lib/route-node.js

@@ -1,14 +1,17 @@
 'use strict'
 var utils = require('./utils')
 
-var noop = utils.noop
 var assign = utils.assign
+var isFunction = utils.isFunction
+var isRegExp = utils.isRegExp
 var isString = utils.isString
+var noop = utils.noop
 
 function RouteNode (options) {
   options = options || {}
   this._children = Object.create(null)
   this._regExs = Object.create(null)
+  this._funcs = Object.create(null)
 }
 
 assign(RouteNode.prototype, {
@@ -29,8 +32,10 @@ assign(RouteNode.prototype, {
 
     if (isString(part)) {
       node = this._children[part]
-    } else {
+    } else if (isRegExp(part)) {
       this._regExs[part] = part
+    } else if (isFunction(part)) {
+      this._funcs[part] = part
     }
 
     if (node == null) {
@@ -56,42 +61,54 @@ assign(RouteNode.prototype, {
       if (results && results.node) {
         return results.node.get(parts, args.concat(results.args), done)
       } else {
-        return done(new Error('not found'))
+        results = this._getFunctionChild(part)
+        if (results && results.node) {
+          return results.node.get(parts, args.concat(results.args), done)
+        } else {
+          return done(new Error('not found'))
+        }
       }
     }
   },
 
   _getRegexChild: function _getRegexChild(part) {
-    var childKey = null
-    var args = []
     var self = this
 
-    Object.keys(this._regExs).forEach(function checkRegex(key) {
-      if (childKey) {
-        return
+    return Object.keys(this._regExs).reduce(function checkRegex(memo, key) {
+      if (memo) {
+        return memo
       }
       var regex = self._regExs[key]
       var results = regex.exec(part)
-      var lastIndex = null
-      if (results) {
-        childKey = key
+      if (!results) {
+        return null
       }
+
+      var lastIndex = null
+      var args = []
       while (results && results.index !== lastIndex) {
         args = args.concat(results[0])
         lastIndex = results.index
         results = regex.exec(part)
       }
-    })
+      return {args: args, key: key, node: self._children[key]}
+    }, null)
+  },
 
-    if (childKey) {
-      return {
-        args: args,
-        key: childKey,
-        node: this._children[childKey]
+  _getFunctionChild: function _getFunctionChild(part) {
+    var self = this
+    return Object.keys(self._funcs).reduce(function checkFunc(memo, key) {
+      if (memo) {
+        return memo
       }
-    } else {
-      return null
-    }
+      var func = self._funcs[key]
+      var result = func(part)
+      if (result) {
+        return {args: [result], key: key, node: self._children[key]}
+      } else {
+        return null
+      }
+    }, null)
   }
 
 })

lib/utils.js

@@ -31,8 +31,8 @@ function checkType(type) {
   }
 }
 
-// add isRegExp, isArray
-['RegExp', 'Array'].forEach(function addIsChecks(type) {
+// add isRegExp, isArray, isFunction
+['RegExp', 'Array', 'Function'].forEach(function addIsChecks(type) {
   utils['is' + type] = checkType(type)
 })
 

test/route-node.js

@@ -58,5 +58,25 @@ module.exports = describe('RouteNode', function () {
       })
     })
 
+    it('→ get route with function', function (done) {
+      function toInt(part) {
+        var results = /^(\d+)$/.exec(part)
+        if (results) {
+          return parseInt(results[0], 10)
+        } else {
+          return null
+        }
+      }
+
+      node.add(['by', 'id', toInt], callback, context)
+      node.get(['by', 'id', '123'], [], function (err, func, cbContext, args) {
+        expect(err).toBe(null, err && err.message)
+        expect(func).toBe(callback)
+        expect(cbContext).toBe(context)
+        expect(args).toEqual([123])
+        done()
+      })
+    })
+
   })
 })

test/router.js

@@ -75,4 +75,25 @@ describe('Router', function () {
       done()
     })
   })
+
+  it('→ get based on function', function (done) {
+    function toInt(part) {
+      var results = /^(\d+)$/.exec(part)
+      if (results) {
+        return parseInt(results[0], 10)
+      } else {
+        return null
+      }
+    }
+
+    var router = new Router()
+    router.add(['by', 'order', toInt], function (val) {
+      expect(val).toBe(123)
+    })
+
+    router.route('/by/order/123', function (err) {
+      expect(err).toBe(null, err && err.message)
+      done()
+    })
+  })
 })

test/utils.js

@@ -4,6 +4,7 @@ var utils = require('../lib/utils')
 var assign = utils.assign
 var forEach = utils.forEach
 var isArray = utils.isArray
+var isFunction = utils.isFunction
 var isRegExp = utils.isRegExp
 var isString = utils.isString
 var noop = utils.noop
@@ -58,6 +59,24 @@ describe('utils', function () {
     })
   })
 
+  describe('→ isFunction', function () {
+    it('→ true for function', function () {
+      expect(isFunction(function () {})).toBe(true)
+    })
+
+    it('→ false for array', function () {
+      expect(isFunction([])).toBe(false)
+    })
+
+    it('→ false for regex', function () {
+      expect(isFunction(/some regex/)).toBe(false)
+    })
+
+    it('→ false for strings', function () {
+      expect(isFunction('some string')).toBe(false)
+    })
+  })
+
   describe('→ forEach', function () {
     it('→ does not call properties on prototype', function () {
       var count = 0