8025520: Array.prototype.slice should only copy defined elements

Reviewed-by: sundar, lagergren

1 files changed, 5 insertions, 2 deletions

diff --git a/src/jdk/nashorn/internal/objects/NativeArray.java b/src/jdk/nashorn/internal/objects/NativeArray.java
index 8cb1ded9..0cdc13a5 100644
--- a/src/jdk/nashorn/internal/objects/NativeArray.java
+++ b/src/jdk/nashorn/internal/objects/NativeArray.java
@@ -860,9 +860,12 @@ public final class NativeArray extends ScriptObject {
             return new NativeArray(sobj.getArray().slice(k, finale));
         }
 
-        final NativeArray copy = new NativeArray(0);
+        // Construct array with proper length to have a deleted filter on undefined elements
+        final NativeArray copy = new NativeArray(finale - k);
         for (long n = 0; k < finale; n++, k++) {
-            copy.defineOwnProperty(ArrayIndex.getArrayIndex(n), sobj.get(k));
+            if (sobj.has(k)) {
+                copy.defineOwnProperty(ArrayIndex.getArrayIndex(n), sobj.get(k));
+            }
         }
 
         return copy;