Merge pull request #6 from anttih/is-null

Add `isNull` predicate

Author: garyb

src/JSON.purs

@@ -30,7 +30,7 @@ import Data.Function.Uncurried (runFn2, runFn3, runFn7)
 import Data.Int as Int
 import Data.Maybe (Maybe(..))
 import JSON.Internal (JArray, JObject, JSON)
-import JSON.Internal (JArray, JObject, JSON) as Exports
+import JSON.Internal (JArray, JObject, JSON, isNull) as Exports
 import JSON.Internal as Internal
 
 -- | Attempts to parse a string as a JSON value. If parsing fails, an error message detailing the

src/JSON/Internal.js

@@ -57,3 +57,5 @@ export const _index = (nothing, just, ix, arr) =>
   ix >= 0 && ix < arr.length ? just(arr[ix]) : nothing;
 
 export const _append = (xs, ys) => xs.concat(ys);
+
+export const isNull = (json) => json == null;

src/JSON/Internal.purs

@@ -140,3 +140,5 @@ foreign import _append
        JArray
        JArray
        JArray
+
+foreign import isNull :: JSON -> Boolean

test/Main.purs

@@ -35,6 +35,10 @@ main = do
   assertTrue $ J.fromJObject (JO.fromEntries [ Tuple "a" (J.fromInt 1) ]) == J.fromJObject (JO.fromEntries [ Tuple "a" (J.fromInt 1) ])
   assertTrue $ J.fromJObject (JO.fromEntries [ Tuple "a" (J.fromInt 1) ]) < J.fromJObject (JO.fromEntries [ Tuple "a" (J.fromInt 2) ])
 
+  log "Check isNull"
+  assertTrue $ J.isNull J.null
+  assertTrue $ not $ J.isNull (J.fromInt 1)
+
   log "Check array index"
   assertTrue $ JA.index (-1) (JA.fromArray (J.fromInt <$> [ 0, 2, 4 ])) == Nothing
   assertTrue $ JA.index 0 (JA.fromArray (J.fromInt <$> [ 0, 2, 4 ])) == Just (J.fromInt 0)