diff --git a/builtin_date.go b/builtin_date.go
index 84a80ac0..d676ddd9 100644
--- a/builtin_date.go
+++ b/builtin_date.go
@@ -198,11 +198,25 @@ func (r *Runtime) dateproto_toTimeString(call FunctionCall) Value {
 	panic(r.NewTypeError("Method Date.prototype.toTimeString is called on incompatible receiver"))
 }
 
+func (d *dateObject) withTimeZoneOpts(r *Runtime, call FunctionCall) time.Time {
+	t := d.time()
+	if arg1 := call.Argument(1); arg1 != _undefined {
+		opts := r.toObject(arg1)
+		if tz := opts.Get("timeZone"); tz != nil && tz != _undefined {
+			if loc, err := time.LoadLocation(tz.String()); err == nil {
+				return t.In(loc)
+			}
+		}
+	}
+	return t
+}
+
 func (r *Runtime) dateproto_toLocaleString(call FunctionCall) Value {
 	obj := r.toObject(call.This)
 	if d, ok := obj.self.(*dateObject); ok {
 		if d.isSet() {
-			return asciiString(d.time().Format(datetimeLayout_en_GB))
+			t := d.withTimeZoneOpts(r, call)
+			return asciiString(t.Format(datetimeLayout_en_GB))
 		} else {
 			return stringInvalidDate
 		}
@@ -214,7 +228,8 @@ func (r *Runtime) dateproto_toLocaleDateString(call FunctionCall) Value {
 	obj := r.toObject(call.This)
 	if d, ok := obj.self.(*dateObject); ok {
 		if d.isSet() {
-			return asciiString(d.time().Format(dateLayout_en_GB))
+			t := d.withTimeZoneOpts(r, call)
+			return asciiString(t.Format(dateLayout_en_GB))
 		} else {
 			return stringInvalidDate
 		}
@@ -226,7 +241,8 @@ func (r *Runtime) dateproto_toLocaleTimeString(call FunctionCall) Value {
 	obj := r.toObject(call.This)
 	if d, ok := obj.self.(*dateObject); ok {
 		if d.isSet() {
-			return asciiString(d.time().Format(timeLayout_en_GB))
+			t := d.withTimeZoneOpts(r, call)
+			return asciiString(t.Format(timeLayout_en_GB))
 		} else {
 			return stringInvalidDate
 		}
@@ -989,9 +1005,9 @@ func createDateProtoTemplate() *objectTemplate {
 	t.putStr("toString", func(r *Runtime) Value { return r.methodProp(r.dateproto_toString, "toString", 0) })
 	t.putStr("toDateString", func(r *Runtime) Value { return r.methodProp(r.dateproto_toDateString, "toDateString", 0) })
 	t.putStr("toTimeString", func(r *Runtime) Value { return r.methodProp(r.dateproto_toTimeString, "toTimeString", 0) })
-	t.putStr("toLocaleString", func(r *Runtime) Value { return r.methodProp(r.dateproto_toLocaleString, "toLocaleString", 0) })
-	t.putStr("toLocaleDateString", func(r *Runtime) Value { return r.methodProp(r.dateproto_toLocaleDateString, "toLocaleDateString", 0) })
-	t.putStr("toLocaleTimeString", func(r *Runtime) Value { return r.methodProp(r.dateproto_toLocaleTimeString, "toLocaleTimeString", 0) })
+	t.putStr("toLocaleString", func(r *Runtime) Value { return r.methodProp(r.dateproto_toLocaleString, "toLocaleString", 2) })
+	t.putStr("toLocaleDateString", func(r *Runtime) Value { return r.methodProp(r.dateproto_toLocaleDateString, "toLocaleDateString", 2) })
+	t.putStr("toLocaleTimeString", func(r *Runtime) Value { return r.methodProp(r.dateproto_toLocaleTimeString, "toLocaleTimeString", 2) })
 	t.putStr("valueOf", func(r *Runtime) Value { return r.methodProp(r.dateproto_valueOf, "valueOf", 0) })
 	t.putStr("getTime", func(r *Runtime) Value { return r.methodProp(r.dateproto_getTime, "getTime", 0) })
 	t.putStr("getFullYear", func(r *Runtime) Value { return r.methodProp(r.dateproto_getFullYear, "getFullYear", 0) })
diff --git a/date_test.go b/date_test.go
index a3ef7bab..ed000dfc 100644
--- a/date_test.go
+++ b/date_test.go
@@ -130,6 +130,63 @@ func TestTimezoneOffset(t *testing.T) {
 	testScript(SCRIPT, intToValue(-60), t)
 }
 
+func TestDateLocaleTime(t *testing.T) {
+	const SCRIPT = `
+	var d = new Date(Date.UTC(2012, 11, 20, 3, 0, 0));
+	d.toLocaleString("en-GB");
+	`
+
+	l := time.Local
+	defer func() {
+		time.Local = l
+	}()
+	var err error
+	time.Local, err = time.LoadLocation("Europe/London")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	testScript(SCRIPT, asciiString("12/20/2012, 03:00:00"), t)
+}
+
+func TestDateLocaleTimeZones(t *testing.T) {
+	const SCRIPT = `
+	var d = new Date(Date.UTC(2012, 11, 20, 3, 0, 0));
+	d.toLocaleString("en-GB", { timeZone: "Europe/Berlin" });
+	`
+
+	l := time.Local
+	defer func() {
+		time.Local = l
+	}()
+	var err error
+	time.Local, err = time.LoadLocation("Europe/London")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	testScript(SCRIPT, asciiString("12/20/2012, 04:00:00"), t)
+}
+
+func TestDateUnsupportedOptions(t *testing.T) {
+	const SCRIPT = `
+	var d = new Date(Date.UTC(2012, 11, 20, 3, 0, 0));
+	d.toLocaleString("en-GB", { foo: "bar" });
+	`
+
+	l := time.Local
+	defer func() {
+		time.Local = l
+	}()
+	var err error
+	time.Local, err = time.LoadLocation("Europe/London")
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	testScript(SCRIPT, asciiString("12/20/2012, 03:00:00"), t)
+}
+
 func TestDateValueOf(t *testing.T) {
 	const SCRIPT = `
 	var d9 = new Date(1.23e15);
diff --git a/object.go b/object.go
index 79bd67df..2abcda32 100644
--- a/object.go
+++ b/object.go
@@ -967,6 +967,9 @@ func (o *baseObject) export(ctx *objectExportCtx) interface{} {
 		itemNameStr := itemName.String()
 		v := o.val.self.getStr(itemName.string(), nil)
 		if v != nil {
+			if IsUndefined(v) && o.val.runtime.exportOptions.dropUndefinedKeys {
+				continue
+			}
 			m[itemNameStr] = exportValue(v, ctx)
 		} else {
 			m[itemNameStr] = nil
@@ -1822,3 +1825,16 @@ func (i *privateId) String() string {
 func (i *privateId) string() unistring.String {
 	return privateIdString(i.name)
 }
+
+type exportOptions struct {
+	dropUndefinedKeys bool
+}
+
+type ExportOptions func(*exportOptions)
+
+// WithDropUndefinedKeys configures object exports to drop undefined keys instead of converting to nil.
+func WithDropUndefinedKeys() ExportOptions {
+	return func(opts *exportOptions) {
+		opts.dropUndefinedKeys = true
+	}
+}
diff --git a/object_test.go b/object_test.go
index 45b95bc5..5a46ad90 100644
--- a/object_test.go
+++ b/object_test.go
@@ -314,6 +314,26 @@ func TestExportToSliceNonIterable(t *testing.T) {
 	}
 }
 
+func TestExportDropUndefinedKeys(t *testing.T) {
+	vm := New()
+	vm.SetExportOptions(WithDropUndefinedKeys())
+
+	o := vm.NewObject()
+	o.Set("foo", vm.ToValue("bar"))
+	o.Set("baz", _undefined)
+	var a map[string]any
+	err := vm.ExportTo(o, &a)
+	if err != nil {
+		t.Fatal(err)
+	}
+	if len(a) != 1 {
+		t.Fatalf("a: %v", a)
+	}
+	if a["foo"] != "bar" {
+		t.Fatalf("Unexpected a[foo]: %v", a["foo"])
+	}
+}
+
 func ExampleRuntime_ExportTo_iterableToSlice() {
 	vm := New()
 	v, err := vm.RunString(`
diff --git a/runtime.go b/runtime.go
index 9cccb469..e4fb94a3 100644
--- a/runtime.go
+++ b/runtime.go
@@ -193,6 +193,8 @@ type Runtime struct {
 
 	fieldNameMapper FieldNameMapper
 
+	exportOptions exportOptions
+
 	vm    *vm
 	hash  *maphash.Hash
 	idSeq uint64
@@ -2441,6 +2443,13 @@ func (r *Runtime) SetParserOptions(opts ...parser.Option) {
 	r.parserOptions = opts
 }
 
+// SetExportOptions sets the export options for this Runtime.
+func (r *Runtime) SetExportOptions(opts ...ExportOptions) {
+	for _, o := range opts {
+		o(&r.exportOptions)
+	}
+}
+
 // SetMaxCallStackSize sets the maximum function call depth. When exceeded, a *StackOverflowError is thrown and
 // returned by RunProgram or by a Callable call. This is useful to prevent memory exhaustion caused by an
 // infinite recursion. The default value is math.MaxInt32.