Libraries: Move to Userland/Libraries/

Userland/Libraries/LibJS/Tests/operators/in-operator-basic.js

@@ -0,0 +1,32 @@
+test("in operator with objects", () => {
+    const o = { foo: "bar", bar: undefined };
+    expect("" in o).toBeFalse();
+    expect("foo" in o).toBeTrue();
+    expect("bar" in o).toBeTrue();
+    expect("baz" in o).toBeFalse();
+    expect("toString" in o).toBeTrue();
+});
+
+test("in operator with arrays", () => {
+    const a = ["hello", "friends"];
+    expect(0 in a).toBeTrue();
+    expect(1 in a).toBeTrue();
+    expect(2 in a).toBeFalse();
+    expect("0" in a).toBeTrue();
+    expect("hello" in a).toBeFalse();
+    expect("friends" in a).toBeFalse();
+    expect("length" in a).toBeTrue();
+});
+
+test("in operator with string object", () => {
+    const s = new String("foo");
+    expect("length" in s).toBeTrue();
+});
+
+test("error when used with primitives", () => {
+    ["foo", 123, null, undefined].forEach(value => {
+        expect(() => {
+            "prop" in value;
+        }).toThrowWithMessage(TypeError, "'in' operator must be used on an object");
+    });
+});