Add getProperty method to JSON

src/Parser/JSON.md

@@ -108,6 +108,18 @@ dFoldL f acc (VBool b) = f acc _ (VBool b)
 dFoldL f acc VNull = f acc _ VNull
 ```
 
+Look up a property in an object
+
+```idris
+export
+getProperty : (prop : String) -> (object : JSONValue TObject)
+  -> Maybe (type : JSONType ** JSONValue type)
+getProperty prop (VObject xs) = 
+  case dFind (\_, (key, _) => key == prop) xs of
+    Nothing => Nothing
+    Just (type ** (_, val)) => Just (type ** val)
+```
+
 ## Parsers
 
 We are going to get mutually recursive here. Instead of using a `mutual` block,