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

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);
}