Convert poorly formatted date in javascript

Question

I’m trying to hide open-house listings on my map that have already occurred. The only date information I have looks like this:

Public: Sat Sep 18, 10:00AM-2:00PM

I need to be able to compare this date with today so I can create an if statement to hide expired open-houses.

Using this code I was able to cut off the beginning text:

const str = 'Public: Thu Feb 11, 10:00AM-2:00PM';
const opdate = (str.substr(8));
console.log(opdate); // Displays "Thu Feb 11, 10:00AM-2:00PM"

This is where I am now stuck...I can not figure out how to convert this to another format to be able to compare it to today's date. It is missing the year which I'm sure is going to cause issues towards the end of every year, and it has an end time which really isn't necessary as I just need to compare the actual date to today's date.

How do you want to compare? Just the date, or date and time? How is the year to be calculated (or is it even necessary)? — RobG, Sep 19 '21 at 21:49
why are there the month and day (date) values for opening hours? (which normally should only be dialed in weekday and hours!) — Mister Jojo, Sep 19 '21 at 22:36
@RobG I want to compare the date given to today's date. The time isn't needed at all. The year won't really matter too much until the end of the year...luckily most people do not have open houses during the holiday I guess. — Joey Lawrence, Sep 19 '21 at 22:44

Mister Jojo · Answer 1 · 2021-09-19T23:58:56.997

1

something like that ?

let {open,close} = get_OpenCloseDates('Public: Thu Feb 11, 10:00AM-2:00PM')

console.log( 'open ->', open.toLocaleString() )
console.log( 'close ->', close.toLocaleString() )

function get_OpenCloseDates( str )
  {
  let year   = new Date().getFullYear()
  , [wD,mth,d,h1,m1,h2,m2] = str.substr(8).split(/[\s,-]+|:/)
    ;
  return ({open: cDate(mth,d,h1,m1,year), close: cDate(mth,d,h2,m2,year)})

  function cDate(mth,d,h,m,y) 
    {    
    let mN = new Date(`${mth} 1, ${y}`).getMonth() 
    return new Date( y, mN, +d, +h +(m.includes('PM')?12:0),parseInt(m),0)
    }
  }

edited Sep 19 '21 at 23:58

answered Sep 19 '21 at 18:59

Mister Jojo

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Your first answer got me very close to figuring this out. As I mentioned I just need to convert the date so I can do a if else statement if the date is older than today. `const str = 'Public: Thu Feb 11, 10:00AM-2:00PM'; const [weekday,month,day,h1,h2] = str.substr(8).split(/[\s,-]+/); var d = new Date(); var n = d.getFullYear(); const openhousedate = [month,day, n].join("/"); console.log(openhousedate);` This is where I left off which gives me Feb/11/2021...I just need to get today's date in this same format! – Joey Lawrence Sep 19 '21 at 22:42

RobG · Answer 2 · 2021-09-21T02:33:39.893

You can create a timestamp for the date in the same format as the timestamp you have and see if it's in the string, e.g.

// Return date in format DDD MMM D, e.g. Thu Feb 11
function openHouseFormat(date = new Date()) {
  let {month, weekday, day} = new Intl.DateTimeFormat('en',{
    weekday:'short',
    month: 'short',
    day: 'numeric'
  }).formatToParts(date).reduce((obj, part) => {
    obj[part.type] = part.value;
    return obj;
  }, {});
  return `${weekday} ${month} ${day}`;
}

// Check if date is in string, e.g.
// is Thu Feb 11 in Public: Thu Feb 11, 10:00AM-2:00PM
function isSameDay(openHouseDate, date = new Date()) {
  return new RegExp(openHouseFormat(date)).test(openHouseDate);
}

// Date to test
let openHouseDate = 'Public: Thu Feb 11, 10:00AM-2:00PM';
console.log(isSameDay(openHouseDate, new Date(2021,1,11))); // true
// Test today, i.e. not 2021-02-11
console.log(isSameDay(openHouseDate, new Date())); // false

Instead of a regular expression you could use indexOf, which might be a little more efficient.

Given that the "open house" date is a substring of Date.prototype.toString, you can simplify things to:

function isSameDate(publicString, date = new Date()) {
  return publicString.indexOf(date.toString().slice(0,10)) != -1;
}

// Example
let publicString = 'Public: Sat Sep 18, 10:00AM-2:00PM';
[new Date(2021,8,18), // 18 Sep
 new Date()           // today
].forEach(d => console.log(isSameDate(publicString, d)));

The year really isn't necessary as "Sat Sep 18" will only occur about once every 7 years (the last one was 2014, the next is in 2027).

score 0 · Accepted Answer · answered Sep 20 '21 at 18:52

Okay here is the solution I came up with which was based on @Mister Jojo first suggestion. This takes my poorly formatted date, adds the current year, then compares to today so I can do an if else rule. Thanks for everyone's help. I love this site.

const str = 'Public: Tue Dec 21, 10:00AM-2:00PM';
const [weekday,month,day,h1,h2] = str.substr(8).split(/[\s,-]+/);
var d = new Date();
var n = d.getFullYear();
var openhousedate = [month,day, n].join(" ");
var formatted = openhousedate;
//results in MMM DD YYYY



const javaScriptRelease = Date.parse(formatted);

const javaScriptRelease2 = Date.parse("2021/09/20");
document.write(javaScriptRelease + "<br>");
document.write(javaScriptRelease2 + "<br>");


console.log(javaScriptRelease2);


if (javaScriptRelease2 > javaScriptRelease) {
    document.write(' its in the past ');
} else {
    document.write(' open house is coming up ');
}

`Date.parse("2021/09/20")` is a bad idea, see [*Why does Date.parse give incorrect results?*](https://stackoverflow.com/questions/2587345/why-does-date-parse-give-incorrect-results) — RobG, Sep 21 '21 at 02:20

Convert poorly formatted date in javascript

3 Answers3