CODEWITHSUNDEEP
javascriptjquery
user1765862
user1765862

Reputation: 14145

convert HH:mm to Date object in js

If I have two times presented as strings like

14:10 and 19:02

how can I convert to Date object in order to get substracted value 

var res = date1 - date2;

I tried to parse with 

var date = new Date.parseExact(myDateVar, "HH:mm");

I'm getting

Uncaught TypeError: Date.parseExact is not a constructor

Upvotes: 8

Views: 20490

Answers (6)

Linus J
Linus J

Reputation: 188

If you want it to be based of the current datetime. I found a pretty simple solution to this. Parse out the HH:MM to hours and minutes and then replace current ISO string with regex.

function toDateFromHoursAndMinutesString(time: string) {
    const [hours, minutes] = time.split(':');
    const currentDate = new Date();
    const dateStringIso = currentDate.toISOString();
    const replacedDateStringIso = dateStringIso.replace(/T.*/, `T${parseInt(hours)-1}:${minutes}:00.000Z`);
    return new Date(replacedDateStringIso);
}

Upvotes: 0

Álvaro González
Álvaro González

Reputation: 146410

I would not recommend messing with dates and all their oddities (time zones, bad APIs, daylight saving time, leap seconds...). For instance, if you want to calculate "3:05" - "2:00" and your script happens to run on the day there DST switch happens you may end up with results like 0:05 if you aren't carefull.

Fortunately, it's rather easy to parse a string with a time and convert it to a single unit that's easier to do maths with:

// Most error checking omitted for brevity
const text = "23:59";
const parsed = String(text).match(/^(?<minutes>\d+):(?<seconds>\d+)$/);
if (parsed !== null) {
  const minutes = parseInt(parsed.groups.minutes, 10);
  const seconds = parseInt(parsed.groups.seconds, 10);
  const totalSeconds = 60 * minutes + seconds;
  console.log(
    "Input: %s; Minutes: %d; Seconds: %d; Total seconds: %d",
    text, minutes, seconds, totalSeconds
  );
}

You can calculate the difference between two times by calculating and then subtracting the corresponding totalSeconds. If you wrap this in a custom function or object you'll have something reusable. For example:

// Most error checking omitted for brevity
function toSeconds(text) {
  const parsed = String(text).match(/^(?<minutes>\d+):(?<seconds>\d+)$/);
  if (parsed === null) {
    return null;
  }
  return totalSeconds = 60 * parseInt(parsed.groups.minutes, 10) + parseInt(parsed.groups.seconds, 10);
}

function toMinutesSeconds(totalSeconds) {
  const minutes = Math.floor(totalSeconds / 60);
  const seconds = totalSeconds % 60;
  return String(minutes).padStart(2, "0") + ":" + String(seconds).padStart(2, "0");
}

const from = "14:10";
const to = "19:02";
const differenceInSeconds = toSeconds(to) - toSeconds(from);
console.log(
  "Total seconds: %s; MM:SS: %s",
  differenceInSeconds, toMinutesSeconds(differenceInSeconds)
);

It's also worth noting that, unlike date based solutions, this approach works with arbitrary durations (e.g. running time rather than time of the day).

Upvotes: 3

zgabievi
zgabievi

Reputation: 1202

You have several options:

First option:

var date1 = new Date(null, null, null, 14, 10);
var date2 = new Date(null, null, null, 19, 02);

And you will get real date objects.

Second option:

var date1 = new Date('01/01/1970 14:10');
var date2 = new Date('01/01/1970 19:02');

And you will get same result.

Upvotes: 18

Jon Glazer
Jon Glazer

Reputation: 785

Off the top of my head:

var a="14:10";
var b="19:02";

var date1=new Date("01-01-2017 " + a + ":00");
var date2=new Date("01-01-2017 " + b + ":00");
//diff will be the number of milliseconds between the two times.
var diff = Math.abs(date1 - date2);
alert(diff);

of course this requires that you do its done within the same 24 hour period.

Upvotes: 2

Plaimanus Lueondee
Plaimanus Lueondee

Reputation: 43

Date.parse in javascript

I think new Date.parseExact is in C# so there is no constructor in javascript;

Upvotes: 0

Hajji Tarik
Hajji Tarik

Reputation: 1082

first convert this : 14:10 and 19:02 to date

var
    pieces = "14:02".split(':')
    minute, second;

if(pieces.length === 2) {
    minute = parseInt(pieces[0], 10);
    second = parseInt(pieces[1], 10);
}

and use this :

var date1 = new Date("7/13/2010");
var date2 = new Date("12/15/2010");
var timeDiff = Math.abs(date2.getTime() - date1.getTime());
var diffDays = Math.ceil(timeDiff / (1000 * 3600 * 24)); 
alert(diffDays);

Upvotes: 0

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