LibJS: Do not trim whitespace from property names when they're numbers

Fixes #7803.

2 files changed, 8 insertions, 1 deletions

diff --git a/Userland/Libraries/LibJS/Runtime/PropertyName.h b/Userland/Libraries/LibJS/Runtime/PropertyName.h
index 42278ae62b..162059948d 100644
--- a/Userland/Libraries/LibJS/Runtime/PropertyName.h
+++ b/Userland/Libraries/LibJS/Runtime/PropertyName.h
@@ -111,7 +111,7 @@ public:
     bool try_coerce_into_number()
     {
         VERIFY(m_string_may_be_number);
-        i32 property_index = m_string.to_int().value_or(-1);
+        i32 property_index = m_string.to_int(TrimWhitespace::No).value_or(-1);
         if (property_index < 0) {
             m_string_may_be_number = false;
             return false;
diff --git a/Userland/Libraries/LibJS/Tests/builtins/Array/array-index-number-whitespace.js b/Userland/Libraries/LibJS/Tests/builtins/Array/array-index-number-whitespace.js
new file mode 100644
index 0000000000..d45cf6dd58
--- /dev/null
+++ b/Userland/Libraries/LibJS/Tests/builtins/Array/array-index-number-whitespace.js
@@ -0,0 +1,7 @@
+test("indexing the array doesn't strip whitespace if it's a number", () => {
+    var a = [];
+    a[1] = 1;
+
+    expect(a["1"]).toBe(1);
+    expect(a[" 1 "]).toBeUndefined();
+});