当前位置：首页 > 资讯 > 技术文档

深入理解javascript的getTime()方法

时间：2020-09-02 18:10 编辑：来源：阅读：
扫一扫，手机访问

摘要：深入理解javascript的getTime()方法

[b]1、理解getTime[/b] [code]getTime() [/code]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： [img]http://files.jb51.net/file_images/article/201702/2017021623305311.png[/img] 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） [img]http://files.jb51.net/file_images/article/201702/2017021623305312.png[/img] [b]2、应用场景[/b] 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： [img]http://files.jb51.net/file_images/article/201702/2017021623305413.png[/img] 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 [b]3、浏览器的兼容性[/b] 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： [img]http://files.jb51.net/file_images/article/201702/2017021623305414.png[/img] [img]http://files.jb51.net/file_images/article/201702/2017021623305415.png[/img] [b]4、参考资料[/b] Date.prototype.getTime()：[url=https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Date/getTime]https://developer.mozilla.org/zh-CN/docs/Web/JavaScript/Reference/Global_Objects/Date/getTime[/url]

全部评论(0)

上一篇：关于Aptana Studio生成自动备份文件的解决办法
下一篇：js 第二代身份证号码的验证机制代码

资讯排行榜
更多>>