The problem of getting and working with dates in Js

Question

When working with the task, it became necessary to get dates from html, and to find out the time difference between them:

var now_time_div = document.getElementById("time_now_of");
var start_time_div = document.getElementById("time_when_start_of");

var time_now = now_time_div.textContent || now_time_div.innerHTML;
var time_start = start_time_div.textContent || start_time_div.innerHTML;

After that, without thinking about the format of the data, I wanted to find the time difference in ms:

var worked_time = time_now - time_start

That didn't work, because we are working with a string. After entering the directory, I found the Date.parse() function, which returns the amount of time that has passed since the given date:

var worked_time = Date.parse(time_start);

but it turned out that it works only with a correctly submitted strig, for example We need to have:

Date.parse('01 Jan 1970 00:00:00 GMT');

We have:

Date.parse('21.09.2022, 15:34:21')

Maybe someone knows an easy way to implement this without rebuilding the string?

ISO 8601 (YYYY-MM-DDTHH:mm:ss.sssZ) is the only date format explicitly specified to be supported, though most browsers seem to support a wide range of alternatives. Question: What is the source of the dates in the html, i.e., is this is user input or generated by the server or a script? — Yogi, Sep 21 '22 at 13:11
It is generated on the site with which the program should work — Ivan Mishakivskiy, Sep 21 '22 at 13:16
@yogi—there are [two others](https://262.ecma-international.org/13.0/#sec-date.parse): the formats produced by *toString* and *toUTCString*. ;-) — RobG, Sep 22 '22 at 07:56

score 1 · Accepted Answer · answered Sep 21 '22 at 13:30

1

If you don't want to bring in a library like moment.js, you can just massage the date string a bit so it can be parsed correctly

const dateString = '21.09.2022, 15:34:21';
const curDate = dateString.split(',')[0].substring(0, 10).split('.');
const curTime = dateString.split(',')[1];
const parsed = `${curDate[1]}'/'${curDate[0]}'/'${curDate[2]} ${curTime}`;
console.log(new Date(parsed).toString()); // Properly formatted date

You can used this parsed variable to compare to other properly formatted dates

answered Sep 21 '22 at 13:30

tuckermassad

126
4

This substitutes one unsupported format with another. If you’re going to parse the string, do it properly and either generate a supported format or pass the values for year, month, day, etc. directly to the constructor (which is preferable to parsing twice). – RobG Sep 22 '22 at 07:59

score 0 · Answer 2 · answered Sep 21 '22 at 13:26

You can use moment.js to parse custom date formats just as in for example Java: https://momentjs.com/docs/#/parsing/string-format/

After that you can simply convert it to a js date using the toDate function: https://momentjs.com/docs/#/displaying/as-javascript-date/

Edit Example:

var mDate = moment('2022-09-21 10:15:00', 'YYYY-MM-DD HH:mm:ss');
var jsDate = mDate.toDate();

The problem of getting and working with dates in Js

2 Answers2