使用JS如何獲得當前時間差

/**
 * JS獲取距當前時間差
 * 
 * @param int time 時間戳格式
 *
 */
function get_time_diff(time) {
 var diff = '';
 var time_diff = new Date().getTime() - time; //時間差的毫秒數 
 
 //計算出相差天數 
 var days = Math.floor(time_diff / (24 * 3600 * 1000));
 if (days > 0) {
 diff += days + '天';
 }
 //計算出小時數 
 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';
 }
 }
 //計算相差分鐘數 
 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;
}