Change date from YYYYMMDD to YYYY-MM-DD Javascript

Question

I'm trying to convert a string from my database that is formatted as YYYYMMDD and is placed in the input box id="startingdate". How would I convert it to YYYY-MM-DD at the other input box id="startingdate1"?

<input type="" id="startingdate1" name="startingdate1" size="20" class="form-control col-md-7 col-xs-12" placeholder="YYYY-MM-DD"/>
<input id="startingdate" name="startingdate" type="hidden"/>

@NguyenSyThanhSon—it doesn't seem sensible to load a few thousand lines of library, convert the string to a date, then convert it back to a string again in a slightly different format just to insert two hyphens. — RobG
– RobG, Commented Apr 15, 2016 at 4:26

castletheperson · Accepted Answer · 2016-04-15 04:34:16Z

19

s = s.replace(/(\d{4})(\d{2})(\d{2})/g, '$1-$2-$3');

This uses a regular expression to replace a sequence of four digits, followed by a sequence of two digits, followed by a sequence of two digits, with the first, plus a -, plus the second, plus a -, plus the third.

edited Apr 15, 2016 at 4:34

castletheperson

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answered Apr 15, 2016 at 4:14

Akhilesh Singh

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6 Comments

castletheperson Over a year ago

I just love when I'm trying to solve a problem concerning string manipulation, and then I remember -- "Oh yeah, there's a whole language dedicated to parsing strings"

Akhilesh Singh Over a year ago

@4castle Thank you so much actually i m beginner i m trying to improve my skills thanks for suggestion

wfaye Over a year ago

This didn't work in my js browser console, nor my node console. any reason why?

wfaye Over a year ago

s = "YYYYMMDD"; s = s.replace(/(\d{4})(\d{2})(\d{2})/g, '$1-$2-$3'); console.log(s);

Akhilesh Singh Over a year ago

s = '20160416'; // here use digits insteads of words s = s.replace(/(\d{4})(\d{2})(\d{2})/g, '$1-$2-$3'); // if you want words the replace the d with w console.log(s);

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damo-s · Accepted Answer · 2016-04-15 04:22:14Z

5

Not using a regular expression if for some reason you don't want to:

var startDate = document.getElementById('startingdate').value;
var displayDate = document.getElementById('startingdate1');

var year = startDate.substring(0, 4);
var month = startDate.substring(4, 6);
var day = startDate.substring(6, 8);

displayDate.value = year + '-' + month + '-' + day;

<input type="" id="startingdate1" name="startingdate1" size="20" class="form-control col-md-7 col-xs-12" placeholder="YYYY-MM-DD"/>
<input id="startingdate" name="startingdate" type="hidden" value="20160415"/>

answered Apr 15, 2016 at 4:22

damo-s

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3 Comments

RobG Over a year ago

Or even [s.slice(0, 4), s.slice(4,6), s.slice(6,8)].join('-'). ;-)

castletheperson Over a year ago

@RobG That's actually the best solution to this question, but regex is pretty awesome too.

Hafiz Idris Over a year ago

as a very new programmer, your answer helped me in understanding the logic to handle this problem the most. So, thank you!

wfaye · Accepted Answer · 2016-04-15 04:52:06Z

3

The most reliable way for me so far was:

var a = "YYYYMMDD";
var b = [a.slice(0, 4), "-", a.slice(4, 6), "-", a.slice(6, 8)].join('');
console.log(b);

answered Apr 15, 2016 at 4:52

wfaye

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1 Comment

castletheperson Over a year ago

If you remove the - from inside the array, you can just put .join('-')

Penny Liu · Accepted Answer · 2019-02-11 04:08:52Z

3

Cleaner, simpler version:

function dateFormat(value, pattern) {
  var i = 0,
    date = value.toString();
  return pattern.replace(/#/g, _ => date[i++]);
}
var displayDate = dateFormat('19700101', '####-##-##');
console.log(displayDate);

answered Feb 11, 2019 at 4:08

Penny Liu

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