LibJS: Implement Object.prototype.isPrototypeOf

Spec: https://tc39.es/ecma262/#sec-object.prototype.isprototypeof
Author: https://github.com/Lubrsi Commit: be30dc2b18 Pull-request: https://github.com/SerenityOS/serenity/pull/4590 Reviewed-by: https://github.com/linusg
2025-08-01 13:49:16 +00:00 · 2020-12-28 01:22:38 +00:00 · 2020-12-28 01:22:38 +00:00 · be30dc2b18 · 2024-07-19 00:30:06 +09:00
commit be30dc2b18
parent ee1d9217aa
4 changed files with 40 additions and 0 deletions
--- a/Libraries/LibJS/Tests/builtins/Object/Object.prototype.isPrototypeOf.js
+++ b/Libraries/LibJS/Tests/builtins/Object/Object.prototype.isPrototypeOf.js
@ -0,0 +1,18 @@
+test("basic functionality", () => {
+    function A() {}
+    function B() {}
+
+    A.prototype = new B();
+    const C = new A();
+
+    expect(A.prototype.isPrototypeOf(C)).toBeTrue();
+    expect(B.prototype.isPrototypeOf(C)).toBeTrue();
+
+    expect(A.isPrototypeOf(C)).toBeFalse();
+    expect(B.isPrototypeOf(C)).toBeFalse();
+
+    const D = new Object();
+    expect(Object.prototype.isPrototypeOf(D)).toBeTrue();
+    expect(Function.prototype.isPrototypeOf(D.toString)).toBeTrue();
+    expect(Array.prototype.isPrototypeOf([])).toBeTrue();
+});