如何仅比较日期部分而不比较 JavaScript 中的时间？

要在 javascript 中获取日期和时间，我们有Date()类。我们通过创建对象来访问Date()类。 Date()类返回日期和时间的组合。

实例化日期有四种方法：
句法：

var d = new Date();
//returns the present date and time

或者

var d = new Date(milliseconds);
//to set a specific date

或者

var d = new Date(dateString);
//to set a specific date

或者

var d = new Date(year, month, day, hours, minutes, seconds, milliseconds);
//to set a specific date:

所以 Date() 返回函数Date() { [native code] }我们可以使用object.toString()将其转换为字符串

方法一：
当对象进行比较时，它会与时间和日期进行比较。
所以现在我们将以这种方式将时间设置为 00:00:00（停止），当比较对象时只比较日期，因为两个日期对象的时间都是 00:00:00（停止）。

要将时间设置为 00:00:00（停止）， setHours()就派上用场了。

句法;

//the hour(0-23) is mandatory.
dateobject.setHours(hour, min, sec, millisec)

为了使时间为 0 或完全停止，我们必须确保所有参数都为 0，包括毫秒。

例子：

  

  
    Below date1 and data2 are compared for older, further, and same dates.
  
    
        //Example-1
        var date1 = new Date();
        date1.setHours(0, 0, 0, 0)
        var date2 = new Date(2020, 8, 20);
        //stops the clock
        date2.setHours(0, 0, 0, 0)
        document.write("date1=>", date1);
        document.write("<br \>date2=>", date2);
        if (date1 > date2) {
            document.write("<br \>date1 is further than date2");
        } else if (date1 < date2) {
            document.write("<br \>date1 is older than date2")
        } else {
            document.write("<br \>date1 and date2 same")
        }
        //Example-2
        date2 = new Date(2019, 11, 3);
        document.write("<br \><br \>date1=>", date1);
        document.write("<br \>date2=>", date2);
        if (date1 > date2) {
            document.write("<br \>date1 is further than date2");
        } else if (date1 < date2) {
            document.write("<br \>date1 is older than date2")
        } else {
            document.write("<br \>date1 and date2 same")
        }
        //Example-3
        date1 = new Date();
        date2 = new Date();
        date1.setHours(0, 0, 0, 0)
        date2.setHours(0, 0, 0, 0)
        document.write("<br \><br \>date1=>", date1);
        document.write("<br \>date2=>", date2);
        if (date1 > date2) {
            document.write("<br \>date1 is further than date2");
        } else if (date1 < date2) {
            document.write("<br \>date1 is older than date2")
        } else {
            document.write("<br \>date1 and date2 same.")
        }
        //Example-4
        date1 = new Date();
        date2 = new Date();
        date1.setHours(0, 0, 0, 0)
            /*Due to, time didn't get stop in data2,
            it’s time also gets compared to data1.*/
            //date2.setHours(0,0,0,0)
        document.write("<br \><br \>date1=>", date1);
        document.write("<br \>date2=>", date2);
        if (date1 > date2) {
            document.write("<br \>date1 is further than date2");
        } else if (date1 < date2) {
            document.write("<br \>date1 is older than date2")
        } else {
            document.write("<br \>date1 and date2 same.")
        }
    
  

  

输出

Below date1 and data2 are compared for older, further, and same dates.

date1=>Wed Dec 04 2019 00:00:00 GMT+0530 (India Standard Time)
date2=>Sun Sep 20 2020 00:00:00 GMT+0530 (India Standard Time)
date1 is older than date2

date1=>Wed Dec 04 2019 00:00:00 GMT+0530 (India Standard Time)
date2=>Tue Dec 03 2019 00:00:00 GMT+0530 (India Standard Time)
date1 is further than date2

date1=>Wed Dec 04 2019 00:00:00 GMT+0530 (India Standard Time)
date2=>Wed Dec 04 2019 00:00:00 GMT+0530 (India Standard Time)
date1 and date2 same.

date1=>Wed Dec 04 2019 00:00:00 GMT+0530 (India Standard Time)
date2=>Wed Dec 04 2019 05:37:26 GMT+0530 (India Standard Time)
date1 is older than date2

方法二：
这里我们将使用toDateString()来获取唯一的日期，但是当获取它时会被转换为字符串，因为字符串无法进行比较，我们需要再次转换为日期对象，现在将它们转换回对象时间设置为00:00:00(stops) 。

句法：

var date1 = new Date(new Date().toDateString());

上述语法的分解

new Date().toDateString()
converts the Date object to a string containing only the date part.

new Date(new Date().toDateString()); 
converts it back to Date object setting time to 00:00:00

例子

  

  
    Below date1 and data2 are compared for older,
      further, and same dates.
  
    
        //Example-1
        var date1 = new Date(new Date().toDateString());
        var date2 = new Date(new Date(2018, 8, 20).toDateString());
        //var date2 = new Date(2018,8,20).toDateString();
        document.write("date1=>", date1); //returns only the date.
        document.write("<br \>date2=>", date2);
        if (date1 > date2) {
            document.write("<br \>date1 is further than date2");
        } else if (date1 < date2) {
            document.write("<br \>date1 is older than date2")
        } else {
            document.write("<br \>date1 and date2 same")
        }
    

  

输出

Below date1 and data2 are compared for older, further, and same dates.

date1=>Fri Dec 20 2019 00:00:00 GMT+0530 (India Standard Time)
date2=>Thu Sep 20 2018 00:00:00 GMT+0530 (India Standard Time)
date1 is further than date2