Kintoneの時刻計算をjsで再現

もろもろの事情で計算式使えない時用

こういうのをjsで再現したい

    const time1 = new Date("2025-01-01 00:00");
    const time2 = new Date("2025-01-01 03:30");//このへんはうまく
    let timeDiff = time2.getTime() - time1.getTime();

    let hour = timeDiff / (1000 * 60 * 60);
    let minute = (hour - Math.floor(hour)) * 60;

     let diff = Math.floor(hour) + "時間" + Math.floor(minute) + "分";