how to compare two string dates in javascript?

Question

I have two string dates in the format of m/d/yyyy. For example, “11/1/2012”, “1/2/2013”. I am writing a function in JavaScript to compare two string dates. The signature of my function is bool isLater(string1, string2), if the date passed by string1 is later than the date passed by string2, it will return true, otherwise false. So, isLater(“1/2/2013”, “11/1/2012”) should return true. How do I write a JavaScript function for this?

Answer 1

const d1 = Date.parse("2012-11-01");
const d2 = Date.parse("2012-11-04");

if (d1 < d2) {
  console.log("Error!");
}

Or, as mentioned in the comments, directly compare the strings:

if ("2012-11-01" < "2012-11-04") {
  console.log("Error!");
}

Answer 2

You can simply compare 2 strings

function isLater(dateString1, dateString2) {
  return dateString1 > dateString2
}

Then

isLater("2012-12-01", "2012-11-01")

returns true while

isLater("2012-12-01", "2013-11-01")

returns false

Answer 3

Parse the dates and compare them as you would numbers:

function isLater(str1, str2)
{
    return new Date(str1) > new Date(str2);
}

If you need to support other date format consider a library such as date.js.

Answer 4

Directly parsing a date string that is not in yyyy-mm-dd format, like in the accepted answer does not work. The answer by vitran does work but has some JQuery mixed in so I reworked it a bit.

// Takes two strings as input, format is dd/mm/yyyy
// returns true if d1 is smaller than or equal to d2

function compareDates(d1, d2){
var parts =d1.split('/');
var d1 = Number(parts[2] + parts[1] + parts[0]);
parts = d2.split('/');
var d2 = Number(parts[2] + parts[1] + parts[0]);
return d1 <= d2;
}

P.S. would have commented directly to vitran's post but I don't have the rep to do that.

Answer 5

This worked for me in nextjs/react

import { format, parse, isBefore } from "date-fns";

...

{isBefore(new Date(currentDate), new Date(date)) ? (
 <span>Upcoming Event</span>
) : (
 <span>Past Event</span>
)}

...

isBefore(date, dateToCompare)

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

Answer 6

You can use "Date.parse()" to properly compare the dates, but since in most of the comments people are trying to split the string and then trying to add up the digits and compare with obviously wrong logic -not completely.

Here's the trick. If you are breaking the string then compare the parts in nested format.

Compare year with year, month with month and day with day.

<pre><code>

var parts1 = "26/07/2020".split('/');
var parts2 = "26/07/2020".split('/');

var latest = false;

if (parseInt(parts1[2]) > parseInt(parts2[2])) {
    latest = true;
} else if (parseInt(parts1[2]) == parseInt(parts2[2])) {
    if (parseInt(parts1[1]) > parseInt(parts2[1])) {
        latest = true;
    } else if (parseInt(parts1[1]) == parseInt(parts2[1])) {
        if (parseInt(parts1[0]) >= parseInt(parts2[0])) {
            latest = true;
        } 
    }
}

return latest;

</code></pre>

Answer 7

If your date is not in format standar yyyy-mm-dd (2017-02-06) for example 20/06/2016. You can use this code

var parts ='01/07/2016'.val().split('/');
var d1 = Number(parts[2] + parts[1] + parts[0]);
parts ='20/06/2016'.val().split('/');
var d2 = Number(parts[2] + parts[1] + parts[0]);
return d1 > d2