Add better detection of functions in reduce

reduce.js

@@ -1,12 +1,18 @@
 'use strict'
 
 function reduce(json, code) {
-  if (/^\w+\s*=>/.test(code)) {
-    const fx = eval(code)
-    return fx(json)
+  if (/^\./.test(code)) {
+    const fx = eval(`function fn() { 
+      return ${code === '.' ? 'this' : 'this' + code} 
+    }; fn`)
+    return fx.call(json)
   }
 
-  if (/yield/.test(code)) {
+  if ('?' === code) {
+    return Object.keys(json)
+  }
+
+  if (/yield\*?\s/.test(code)) {
     const fx = eval(`function fn() {
       const gen = (function*(){ 
         ${code.replace(/\\\n/g, '')} 
@@ -16,21 +22,15 @@ function reduce(json, code) {
     return fx.call(json)
   }
 
-  if ('?' === code) {
-    return Object.keys(json)
-  }
-
-  if (/^\./.test(code)) {
-    const fx = eval(`function fn() { 
-      return ${code === '.' ? 'this' : 'this' + code} 
-    }; fn`)
-    return fx.call(json)
-  }
-
   const fx = eval(`function fn() { 
     return ${code} 
   }; fn`)
-  return fx.call(json)
+
+  const fn = fx.call(json)
+  if (typeof fn === 'function') {
+    return fn(json)
+  }
+  return fn
 }
 
 module.exports = reduce

test.js

@@ -12,10 +12,20 @@ test('pass', t => {
 })
 
 test('anon func', t => {
+  const r = fx({"key": "value"}, "'function (x) { return x.key }'")
+  t.deepEqual(r, 'value\n')
+})
+
+test('arrow func', t => {
   const r = fx({"key": "value"}, "'x => x.key'")
   t.deepEqual(r, 'value\n')
 })
 
+test('arrow func ()', t => {
+  const r = fx({"key": "value"}, "'(x) => x.key'")
+  t.deepEqual(r, 'value\n')
+})
+
 test('this bind', t => {
   const r = fx([1, 2, 3, 4, 5], "'this.map(x => x * this.length)'")
   t.deepEqual(JSON.parse(r), [5, 10, 15, 20, 25])