LibJS: Add Date.prototype.setTime()

Userland/Libraries/LibJS/Runtime/CommonPropertyNames.h

@@ -223,6 +223,7 @@ namespace JS {
     P(setMonth)                              \
     P(setPrototypeOf)                        \
     P(setSeconds)                            \
+    P(setTime)                               \
     P(setYear)                               \
     P(shift)                                 \
     P(sign)                                  \

Userland/Libraries/LibJS/Runtime/DatePrototype.cpp

@@ -56,6 +56,7 @@ void DatePrototype::initialize(GlobalObject& global_object)
     define_native_function(vm.names.getSeconds, get_seconds, 0, attr);
     define_native_function(vm.names.setSeconds, set_seconds, 2, attr);
     define_native_function(vm.names.getTime, get_time, 0, attr);
+    define_native_function(vm.names.setTime, set_time, 1, attr);
     define_native_function(vm.names.getTimezoneOffset, get_timezone_offset, 0, attr);
     define_native_function(vm.names.getUTCDate, get_utc_date, 0, attr);
     define_native_function(vm.names.getUTCDay, get_utc_day, 0, attr);
@@ -505,6 +506,29 @@ JS_DEFINE_NATIVE_FUNCTION(DatePrototype::get_time)
     return Value(this_object->time());
 }
 
+JS_DEFINE_NATIVE_FUNCTION(DatePrototype::set_time)
+{
+    auto* this_object = typed_this(vm, global_object);
+    if (!this_object)
+        return {};
+
+    auto new_time_value = vm.argument(0).to_number(global_object);
+    if (vm.exception())
+        return {};
+    if (!new_time_value.is_finite_number()) {
+        this_object->set_is_invalid(true);
+        return js_nan();
+    }
+    auto new_time = new_time_value.as_double();
+
+    this_object->set_is_invalid(false);
+
+    auto new_date_time = Core::DateTime::from_timestamp(static_cast<time_t>(new_time / 1000));
+    this_object->datetime().set_time(new_date_time.year(), new_date_time.month(), new_date_time.day(), new_date_time.hour(), new_date_time.minute(), new_date_time.second());
+    this_object->set_milliseconds(static_cast<i16>(fmod(new_time, 1000)));
+    return Value(this_object->time());
+}
+
 JS_DEFINE_NATIVE_FUNCTION(DatePrototype::get_timezone_offset)
 {
     auto* this_object = typed_this(vm, global_object);

Userland/Libraries/LibJS/Runtime/DatePrototype.h

@@ -37,6 +37,7 @@ private:
     JS_DECLARE_NATIVE_FUNCTION(get_seconds);
     JS_DECLARE_NATIVE_FUNCTION(set_seconds);
     JS_DECLARE_NATIVE_FUNCTION(get_time);
+    JS_DECLARE_NATIVE_FUNCTION(set_time);
     JS_DECLARE_NATIVE_FUNCTION(get_timezone_offset);
     JS_DECLARE_NATIVE_FUNCTION(get_utc_date);
     JS_DECLARE_NATIVE_FUNCTION(get_utc_day);

Userland/Libraries/LibJS/Tests/builtins/Date/Date.prototype.setTime.js

@@ -0,0 +1,47 @@
+test("no arguments", () => {
+    let date = new Date(2021, 0, 1);
+    date.setTime();
+    expect(date.getTime()).toBe(NaN);
+});
+
+test("NaN or undefined as only argument", () => {
+    let date = new Date(2021, 0, 1);
+    date.setTime(NaN);
+    expect(date.getTime()).toBe(NaN);
+
+    date = new Date(2021, 0, 1);
+    date.setTime(undefined);
+    expect(date.getTime()).toBe(NaN);
+
+    date = new Date(2021, 0, 1);
+    date.setTime("a");
+    expect(date.getTime()).toBe(NaN);
+});
+
+test("Timestamp as argument", () => {
+    let date = new Date(2021, 0, 1);
+
+    date.setTime(1622993746000);
+    expect(date.getDate()).toBe(6);
+    expect(date.getMonth()).toBe(5);
+    expect(date.getFullYear()).toBe(2021);
+    expect(date.getUTCHours()).toBe(15);
+    expect(date.getUTCMinutes()).toBe(35);
+    expect(date.getUTCSeconds()).toBe(46);
+    expect(date.getUTCMilliseconds()).toBe(0);
+});
+
+test("Make Invalid Date valid again", () => {
+    let date = new Date(2021, 0, 1);
+    date.setTime(NaN);
+    expect(date.getTime()).toBe(NaN);
+
+    date.setTime(1622993746000);
+    expect(date.getDate()).toBe(6);
+    expect(date.getMonth()).toBe(5);
+    expect(date.getFullYear()).toBe(2021);
+    expect(date.getUTCHours()).toBe(15);
+    expect(date.getUTCMinutes()).toBe(35);
+    expect(date.getUTCSeconds()).toBe(46);
+    expect(date.getUTCMilliseconds()).toBe(0);
+});