性能 - Date.now（）vs Date.getTime（） [英] Performance - Date.now() vs Date.getTime()

问题描述

var timeInMs = Date.now();

每 MDN

vs。

var timeInMs = new Date(optional).getTime();

每 MDN 。

两者之间是否有任何区别，除了语法和在第二个版本中通过可选项设置日期（不是当前）的能力？

Is there any difference between the two, besides the syntax and the ability to set the Date (to not the current) via optional in the second version?

Date.now（）更快 - 查看 jsperf

Date.now() is faster - check out the jsperf

推荐答案

这些都是相同的（编辑语义;使用 .now（），性能稍好一点）：

These things are the same (edit semantically; performance is a little better with .now()):

var t1 = Date.now();
var t2 = new Date().getTime();

然而，任何已经创建的日期实例在构造时（或在其设置的任何时间/日期）被冻结。也就是说，如果你这样做：

However, the time value from any already-created Date instance is frozen at the time of its construction (or at whatever time/date it's been set to). That is, if you do this:

var now = new Date();

然后等待一段时间，随后调用 now.getTime（） 将告知变量设置点的时间。

and then wait a while, a subsequent call to now.getTime() will tell the time at the point the variable was set.

这篇关于性能 - Date.now（）vs Date.getTime（）的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！