How to compare javascript dates (strings) with a specific format

Question

I have two dates in a specific format (strings). I need to verify if the current date is lower than the max allowed date:

var date_current = '03_25_2022';
var date_max = '03_30_2022';

The format will always be m_d_Y. Since these are technically strings, what would be the best way to compare them as dates?

I'm using this function but I'm not sure of the approach:

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

Use split() to split it into month, day, year. Then call new Date() to create a date from it (don't forget to subtract 1 from the month). Then compare the dates. — Barmar
– Barmar, Commented Mar 30, 2022 at 16:04

Ashok · Accepted Answer · 2022-03-30 16:06:02Z

1

You can first convert these string into date object and then compare their timestamp as follow:

function strToDate(str) {
  const splits = str.split('_');
  if (splits.length !== 3) {
    throw Error("Invalid date");
  }
  return new Date(splits[2], parseInt(splits[0]) - 1, splits[1]);
}

let dateCurrent = strToDate('03_25_2022');
let dateMax = strToDate('03_30_2022');

console.log(dateMax.getTime() > dateCurrent.getTime())

answered Mar 30, 2022 at 16:06

Ashok

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4 Comments

Andres SK Over a year ago

This seems better than my current function. Is there an advantage to do this by converting it to a Date object instead of comparing the sum of the number values of the original strings? (i added my current approach to the original post btw)

Ashok Over a year ago

@AndresSK Yes, there are certain use cases for 1_1_2021 and 12_31_2020, your function would say 12_31_2020 is bigger than 1_1_2021. Since sum for 12_31_2020 => 2063 and for 1_1_2021 => 2023.

Jay Buckman Over a year ago

You'd have to weight the parts of the sum for your approach to work: 40*parts[1] + parts[2] + 1000*(parts[0] - 1000) or similar. 12_31_2020 => 1,020,511 and for 1_1_2021 => 1,021,041

Andres SK Over a year ago

@Ashok Completely understood. Just applied your solution and it works. Marked it as the accepted answer, thanks!

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