如何查看日期是在 javascript 之前还是之后？

Question

I'm given a date const date1 = "2020-08-08"

I want to check whether this date is before today or after today

const date1 = "2020-08-08"
const today = new Date()
if(date1 > new Date) {
    console.log("date1 is the future")
} else {
    console.log("date1 is the past")
}

The above code doesn't work but I am trying to do something like that. Is there a way?

Answer 1

Try using getTime()

var date1 = new Date(2020 - 08 - 08);
var today = new Date();  
if (date1.getTime() > today.getTime()) {
  // Date 1 is the Future
} else {
  // Today is the Future
}

or you can compare directly like date1 > today

If you have date as string, then parse using,

var date1 = Date.parse("2020-08-08");

Answer 2

You can extract today and compare:

var now = new Date();
var month = (now.getMonth() + 1);               
var day = now.getDate();
if (month < 10) 
    month = "0" + month;
if (day < 10) 
    day = "0" + day;
var year = now.getFullYear();
var today = year + '-' + month + '-' + day;

You can compare year, month and day separately and see.

Answer 3

Here's a working snippet to get you started:

 let date1 = Date.parse("2020-08-08"); let today = new Date(); if (date1 < today) { console.log("Date1 is in the past"); } else { console.log("Date1 is in the future"); }

Answer 4

You can use the date-fns library for date comparisions.

https://date-fns.org/v2.15.0/docs/isBefore

https://date-fns.org/v2.15.0/docs/isAfter

isAfter(date1, today);

Answer 5

In if (date1 > new Date) the expression new Date returns a string, so you're effectively comparing '2020-08-08' > new Date().toString() . Since both operands are strings, they will be compared lexically and since the lefthand string starts with a number and the righthand string will always start with a letter, the result will always be false.

What you probably mean to do is:

const date1 = "2020-08-08";
const today = new Date();
if (date1 > today) {
    console.log("date1 is the future");
}

However, '2020-08-08' will be parsed as UTC, so on 8 August the test may return true or false depending on the host system offset setting and the time that the code is executed. See Why does Date.parse give incorrect results?