如何利用js语法计算时间

加法运算：

var date = new Date(2023, 5, 17, 12, 34, 56);
var nextSecond = new Date(date.getTime() + 1000);
console.log('输出结果：', nextSecond)
//输出结果： Sat Jun 17 2023 12:34:57 GMT+0800 (中国标准时间)

减法运算：

var date1 = new Date(2023, 5, 17, 12, 34, 56);
var date2 = new Date(2023, 5, 18, 12, 34, 56);
var diff = date2.getTime() - date1.getTime();
console.log('输出结果：', diff)
//输出结果： 86400000

时间间隔计算：

var date = new Date(2023, 5, 17, 12, 34, 56);
var now = new Date();
var yearDiff = now.getFullYear() - date.getFullYear();
var monthDiff = now.getMonth() - date.getMonth();
var dayDiff = now.getDate() - date.getDate();
var hourDiff = now.getHours() - date.getHours();
var minuteDiff = now.getMinutes() - date.getMinutes();
var secondDiff = now.getSeconds() - date.getSeconds();
var millisecondDiff = now.getMilliseconds() - date.getMilliseconds();
console.log('输出yearDiff结果：', yearDiff) // 0
console.log('输出monthDiff结果：', monthDiff) // -1
console.log('输出dayDiff结果：', dayDiff) // 0
console.log('输出hourDiff结果：', hourDiff) // 11
console.log('输出minuteDiff结果：', minuteDiff) // -33
console.log('输出secondDiff结果：', secondDiff) // -25
console.log('输出millisecondDiff结果：', millisecondDiff) // 946