JS計算距當前時間的時間差

/**
 * JS獲取距當前時間差
 * 
 * @param int time JS毫秒時間戳
 *
 */
function get_time_diff(time) {
    var diff = '';
    var time_diff = new Date().getTime() - time;
    // 計算相差天數  
    var days = Math.floor(time_diff / (24 * 3600 * 1000));
    if (days > 0) {
        diff += days + '天';
    }
    // 計算相差小時數  
    var leave1 = time_diff % ( 24 * 3600 * 1000); 
    var hours = Math.floor(leave1 / (3600 * 1000));
    if (hours > 0) {
        diff += hours + '小時';
    } else {
        if (diff !== '') {
            diff += hours + '小時';
        }
    }
    // 計算相差分鍾數  
    var leave2 =leave1 % (3600 * 1000);
    var minutes = Math.floor(leave2 / (60 * 1000));
    if (minutes > 0) {
        diff += minutes + '分';
    } else {
        if (diff !== '') {
            diff += minutes + '分';
        }
    }
    // 計算相差秒數  
    var leave3 = leave2%(60*1000);
    var seconds = Math.round(leave3/1000);
    if (seconds > 0) {
        diff += seconds + '秒';
    } else {
        if (diff !== '') {
            diff += seconds + '秒';
        }
    }
    
    return diff;
}