LibJS: Reorganize tests into subfolders

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

@@ -0,0 +1,35 @@
+load("test-common.js");
+
+try {
+    ["foo", 123, null, undefined].forEach(value => {
+        assertThrowsError(() => {
+            "prop" in value;
+        }, {
+            error: TypeError,
+            message: "'in' operator must be used on an object"
+        });
+    });
+
+    var o = {foo: "bar", bar: undefined};
+    assert("" in o === false);
+    assert("foo" in o === true);
+    assert("bar" in o === true);
+    assert("baz" in o === false);
+    assert("toString" in o === true);
+
+    var a = ["hello", "friends"];
+    assert(0 in a === true);
+    assert(1 in a === true);
+    assert(2 in a === false);
+    assert("0" in a === true);
+    assert("hello" in a === false);
+    assert("friends" in a === false);
+    assert("length" in a === true);
+
+    var s = new String("foo");
+    assert("length" in s);
+
+    console.log("PASS");
+} catch (e) {
+    console.log("FAIL: " + e);
+}