深入理解javascript的getTime()方法

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：

    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）

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：

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：

4、参考资料

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

# javascript  # getTime  # JavaScript中的getTimezoneOffset()方法使用详解  # JavaScript中的getTime()方法使用详解  # 返回值  # 执行时间  # 都是  # 是一个  # 类库  # 两次  # 甘特图  # 涉及到  # 参考资料  # 这可  # 创建一个  # 使用这个  # 进行测试  # 数据存储  # 而该  # 整型  # 器中  # 结束时间  # 格林威治时间  # Operation 

相关文章： 建站之星如何快速更换网站模板？  如何撰写建站申请书？关键要点有哪些？  linux top下的 minerd 木马清除方法  网站微信制作软件,如何制作微信链接？  建站主机与服务器功能差异如何区分？  Dapper的Execute方法的返回值是什么意思 Dapper Execute返回值详解  山东网站制作公司有哪些,山东大源集团官网？  详解jQuery停止动画——stop()方法的使用  南京网站制作费用,南京远驱官方网站？  如何正确下载安装西数主机建站助手？  如何高效利用200m空间完成建站？  网站海报制作教学视频教程,有什么免费的高清可商用图片网站，用于海报设计？  建站之星如何助力企业快速打造五合一网站？  定制建站平台哪家好？企业官网搭建与快速建站方案推荐  如何快速生成可下载的建站源码工具？  建站之星手机一键生成：多端自适应+小程序开发快速建站指南  北京企业网站设计制作公司,北京铁路集团官方网站？  如何快速搭建支持数据库操作的智能建站平台？  如何访问已购建站主机并解决登录问题？  购物网站制作费用多少,开办网上购物网站，需要办理哪些手续？  唐山网站制作公司有哪些,唐山找工作哪个网站最靠谱？  北京专业网站制作设计师招聘,北京白云观官方网站？  制作充值网站的软件,做人力招聘为什么要自己交端口钱？  公司网站制作费用多少,为公司建立一个网站需要哪些费用？  建站DNS解析失败？如何正确配置域名服务器？  网站插件制作软件免费下载,网页视频怎么下到本地插件？  建站之星如何快速解决建站难题？  高性能网站服务器配置指南：安全稳定与高效建站核心方案  公众号网站制作网页,微信公众号怎么制作？  建站之星Pro快速搭建教程：模板选择与功能配置指南  ,柠檬视频怎样兑换vip？  网站制作公司排行榜,抖音怎样做个人官方网站  网站设计制作公司地址,网站建设比较好的公司都有哪些？  建站主机服务器选购指南：轻量应用与VPS配置解析  建站之星代理如何优化在线客服效率？  如何配置IIS站点权限与局域网访问？  网站制作说明怎么写,简述网页设计的流程并说明原因？  mc皮肤壁纸制作器,苹果平板怎么设置自己想要的壁纸我的世界？  网站设计制作企业有哪些,抖音官网主页怎么设置？  网站制作专业公司有哪些,如何制作一个企业网站，建设网站的基本步骤有哪些？  如何通过PHP快速构建高效问答网站功能？  建站之星logo尺寸如何设置最合适？  微信推文制作网站有哪些,怎么做微信推文，急？  打鱼网站制作软件,波克捕鱼官方号怎么注册？  视频网站app制作软件,有什么好的视频聊天网站或者软件？  如何在宝塔面板中修改默认建站目录？  宁波免费建站如何选择可靠模板与平台？  巅云智能建站系统：可视化拖拽+多端适配+免费模板一键生成  番禺网站制作公司哪家值得合作,番禺图书馆新馆开放了吗？  香港服务器WordPress建站指南：SEO优化与高效部署策略