1 files changed, 36 insertions, 0 deletions
diff --git a/js/src/tests/test262/built-ins/Array/prototype/at/returns-item-relative-index.js b/js/src/tests/test262/built-ins/Array/prototype/at/returns-item-relative-index.js
new file mode 100644
index 0000000000..e131ef40fb
--- /dev/null
+++ b/js/src/tests/test262/built-ins/Array/prototype/at/returns-item-relative-index.js
@@ -0,0 +1,36 @@
+// Copyright (C) 2020 Rick Waldron. All rights reserved.
+// This code is governed by the BSD license found in the LICENSE file.
+/*---
+esid: sec-array.prototype.at
+description: >
+  Returns the item value at the specified relative index
+info: |
+  Array.prototype.at ( )
+
+  Let O be ? ToObject(this value).
+  Let len be ? LengthOfArrayLike(O).
+  Let relativeIndex be ? ToInteger(index).
+  If relativeIndex ≥ 0, then
+    Let k be relativeIndex.
+  Else,
+    Let k be len + relativeIndex.
+  If k < 0 or k ≥ len, then return undefined.
+  Return ? Get(O, ! ToString(k)).
+
+features: [Array.prototype.at]
+---*/
+assert.sameValue(
+  typeof Array.prototype.at,
+  'function',
+  'The value of `typeof Array.prototype.at` is expected to be "function"'
+);
+
+let a = [1, 2, 3, 4, ,5];
+
+assert.sameValue(a.at(0), 1, 'a.at(0) must return 1');
+assert.sameValue(a.at(-1), 5, 'a.at(-1) must return 5');
+assert.sameValue(a.at(-2), undefined, 'a.at(-2) returns undefined');
+assert.sameValue(a.at(-3), 4, 'a.at(-3) must return 4');
+assert.sameValue(a.at(-4), 3, 'a.at(-4) must return 3');
+
+reportCompare(0, 0);