Add `?` shortcut

README.md

@@ -131,6 +131,12 @@ $ cat package.json | fx 'Object.keys(this.dependencies)'
 ]
 ```
 
+By the way, fx has shortcut for `Object.keys(this)`. Previous example can be rewritten as:
+
+```
+$ cat package.json | fx this.dependencies ?
+``` 
+
 
 ## Related
 

index.js

@@ -55,6 +55,8 @@ function reduce(json, code) {
       }; fn
     `)
     return fx.call(json)
+  } else if (/^\?$/.test(code)) {
+    return Object.keys(json)
   } else {
     const fx = eval(`function fn() { return ${code} }; fn`)
     return fx.call(json)