当前位置：主页 > javascript教程 >

深入理解javascript的getTime()方法

  • 更新时间：2022-06-23 11:52:15
  • 编辑：桂元白

1、理解getTime

getTime() 方法返回一个时间的格林威治时间数值。

可以使用这个方法把一个日期时间赋值给另一个Date 对象。

语法：

dateObj.getTime()
参数：

无。

返回值：

getTime 方法的返回值一个数值，表示从1970年1月1日0时0分0秒（UTC，即协调世界时）距离该日期对象所代表时间的毫秒数。

例子：

使用 getTime() 复制日期对象

创建一个拥有相同时间值的日期对象。

var birthday = new Date(1994, 12, 10);
var copy = new Date();
copy.setTime(birthday.getTime());

测试结果如下：

深入理解javascript的getTime()方法

    既然表示从1970年1月1日开始计算的毫秒数，如果小于1970年呢，会是什么情况？（测试结果如下，是负数）

深入理解javascript的getTime()方法

2、应用场景

2.1 测量代码执行时间

连续调用两个新生成的日期对象的 getTime 方法，根据两次调用的返回值求得时间差。这可以用于计算某些操作的执行时间。

var end, start, i;
start = new Date();
for (i = 0; i < 100000; i++) {
 Math.sqrt(i);
}
end = new Date();

console.log("Operation took " + (end.getTime() - start.getTime()) + " msec");

在chrome浏览器中进行测试：

深入理解javascript的getTime()方法

2.2 甘特图时间表示

最近在调整teamwork gantt中，发现，是一个task任务项的开始时间与结束时间，都是用一个整数表示，而该数值就是UTC表示法。格式如下：

{"tasks":[
   {"id":-1,"name":"Gantt editor","code":"","level":0,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":21,"end":1399672799999,"startIsMilestone":true,"endIsMilestone":false,"collapsed":false,"assigs":[],"hasChild":true}
   ,{"id":-2,"name":"coding","code":"","level":1,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":10,"end":1398203999999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"description":"","progress":0,"hasChild":true}
   ,{"id":-3,"name":"gantt part","code":"","level":2,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":2,"end":1397167199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-4,"name":"editor part","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1397167200000,"duration":4,"end":1397685599999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-5,"name":"testing","code":"","level":1,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":6,"end":1399672799999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","description":"","progress":0,"hasChild":true}
   ,{"id":-6,"name":"test on safari","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":2,"end":1399327199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"8SF:11","hasChild":false}
   ,{"id":-7,"name":"test on safari","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":2,"end":1399327199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"8SF","hasChild":false}
   ,{"id":-8,"name":"test on ie","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1400688000000,"duration":3,"end":1400947199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-9,"name":"test on chrome","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1399327200000,"duration":2,"end":1399499999999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"links":"","hasChild":false}
   ,{"id":-10,"name":"Gantt editor","code":"","level":0,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":21,"end":1399672799999,"startIsMilestone":true,"endIsMilestone":false,"collapsed":false,"assigs":[],"hasChild":true}
   ,{"id":-11,"name":"coding","code":"","level":1,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":10,"end":1398203999999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"description":"","progress":0,"hasChild":true}
   ,{"id":-12,"name":"gantt part","code":"","level":2,"status":"STATUS_ACTIVE","canWrite":true,"start":1396994400000,"duration":2,"end":1397167199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-14,"name":"editor part","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1397167200000,"duration":4,"end":1397685599999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-15,"name":"testing","code":"","level":1,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":6,"end":1399672799999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","description":"","progress":0,"hasChild":true}
   ,{"id":-16,"name":"test on safari","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1398981600000,"duration":2,"end":1399327199999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-17,"name":"test on ie","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1399327200000,"duration":3,"end":1399586399999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ,{"id":-18,"name":"test on chrome","code":"","level":2,"status":"STATUS_SUSPENDED","canWrite":true,"start":1399327200000,"duration":2,"end":1399499999999,"startIsMilestone":false,"endIsMilestone":false,"collapsed":false,"assigs":[],"depends":"","hasChild":false}
   ],"selectedRow":0,"canWrite":true,"canWriteOnParent":true}

在甘特图中，使用getTime表示时间有以下优势：

计算两个时间差比较方便
数据存储结构比较简单
由于gantt涉及到画图，使用整型数据方便处理

3、浏览器的兼容性

使用js要收到浏览器的限制，不同浏览器对js类库的支持强弱也不同。而作为标准类库Date的一个方法，其适应的浏览器如下：

深入理解javascript的getTime()方法

深入理解javascript的getTime()方法

4、参考资料

Date.prototype.getTime()：https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Date/getTime

相关教程

  • Javascript操作dom对象之select详解

    下面小编就为大家带来一篇Javascript操作dom对象之select全面解析。小编觉得挺不错的，现在就分享给大家，也给大家做个参考。一起跟随小编过来看看吧

    发布时间：2020-03-11

  • JavaScript Canvas绘制圆形时钟效果代码实例

    这篇文章主要为大家详细介绍了JavaScript Canvas绘制圆形时钟效果的相关资料，具有一定的参考价值，感兴趣的小伙伴们可以参考一下

    发布时间：2020-03-17

  • 详解javascript正则表达式

    这篇文章主要介绍了javascript正则表达式总结,都是些常用的表达式，这里分享给大家，希望大家能够喜欢

    发布时间：2020-01-24

  • jQuery中read和JavaScript中的onload函数的区别总结

    这篇文章主要介绍了jQuery中的read和JavaScript中的onload函数的区别,这两个函数在web编程中是最常用的,一定要搞清楚它们的区别,需要的朋友可以参考下

    发布时间：2019-11-12

  • JavaScript中Promise使用

    Promise，相信每一个前端工程师都或多或少地在项目中都是用过，毕竟它早已不是一个新名词。ES6中已经原生对它加以支持，在caniuse中搜索一下 Promise ，发现新版的chrome和firefox也已经支持。但是

    发布时间：2020-01-27

  • JavaScript实现图片连播以及联级菜单的知识点

    这篇文章主要介绍了基于JavaScript实现图片连播和联级菜单实例代码,非常不错，具有参考借鉴价值，需要的朋友可以参考下

    发布时间：2020-01-07

  • 如何处理jQuery符号$与其他javascript 库、框架冲突的问题

    下面小编就为大家带来一篇完美解决jQuery符号$与其他javascript 库、框架冲突的问题。小编觉得挺不错的，现在就分享给大家，也给大家做个参考。一起跟随小编过来看看吧

    发布时间：2020-01-13

用户留言

发布评论

最新更新

热门推荐