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javascript format date from DDMMYYYY to DD/MM/YYYY

I have a datepicker and I want to parse the date to dd/mm/yyyy when user input is ddmmyyyy.
Image
I have add a javascript function to the input text but I don't know if I am on the right way
<inputText id="input1" onchange="parseDate()"/>
<script type="text/javascript">
$(document).ready(function() {
$("#input1").datepicker()
};
function parseDate() {
???
}
<script>
Thanks

If that's the exact format you're looking at, then you could just parse it out:
http://jsfiddle.net/q3yrtu0z/
$('#input1').change(function() {
$(this).val($(this).val().replace(/^(\d{2})(\d{2})(\d{4})$/, '$1/$2/$3'));
});
This is designed such that if the value is exactly 8 digits, then it will format it XX/XX/XXXX.
You may want to do additional validation on the validity of the date format (although you'd have to do this for MM/DD/YYYY inputs as well anyway)

Try this....
function convertDate(inputFormat) {function pad(s) { return (s < 10) ? '0' + s : s; } var d = new Date(inputFormat); return [pad(d.getDate()), pad(d.getMonth()+1), d.getFullYear()].join('/'); }

As you're going for a simple transformation, consider sliceing your String to the points where you want to add your characters, for example
var strA = '13102015',
strB = strA.slice(0, 2) + '/' + strA.slice(2, 4) + '/' + strA.slice(4);
strB; // "13/10/2015"
As this may be invoked multiple times if the user modifies it later, you may also wish to force the input into expected formatting at the start using replace, e.g.
'13/102015'.replace(/[^\d]/g, ''); // "13102015"
// now continue to slice
In a RegExp,
[chars] means match these characters (in this case c, h, a, r, s)
[^chars] is the inverse of [chars], i.e. match any character except these characters
\d is any digit, i.e. the numbers 0 to 9
The g flag means global, i.e. after a match keep looking for another match

How can I disallow lenient dates in javascript?

I'm trying to validate if a string is a valid date. Date.parse(dateString) or new Date(dateString) both are very lenient. For example a date like 14/14/2000 is coming out as 2/14/2001. I tried a regular expression but now I'm needing to validate more than mm/dd/yyyy, I also need to validate yyyy-mm-ddThh:mm:ss e.g. 1951-02-05T00:00:00.
I was using regular expressions and some basic date checks right now, but the second date format above is failing the regex.
function isDate(dateToCheck) {
if (dateToCheck == "" || dateToCheck == null) { return true; }
var timestamp = Date.parse(dateToCheck);
var d = new Date(timestamp);
var re = /(0[1-9]|1[012])[- \/.](0[1-9]|[12][0-9]|3[01])[- \/.](19|20)\d\d/;
var valid = re.test(dateToCheck);
valid = valid && !isNaN(timestamp);
valid = valid && d.getFullYear() > 1900 && d.getFullYear() < 2100;
return valid;
}
The regex is specifically for mm/dd/yyyy where month and day are both double digits (single digit months get a leading zero) and won't allow invalid months or days like 14 as a month or 32 as a day. The year can be anything from 1900 to 2099.
It's not air tight. It would allow 02/31/2000 which is invalid because February never has 31 days.
How can I validate both of these date formats without allowing lenient dates?

Look at moment.js, and all their parsing options.
http://momentjs.com/docs/#/parsing/string/
Their is an isValid() function that you can use to validate if the input string was correct.
moment("not a real date").isValid(); // false
If you combing that with a date validation string then you get the result you are looking for:
http://momentjs.com/docs/#/parsing/string-formats/
var m = moment('14/14/2000', 'DD/MM/YYYY');
console.log(m.toString(),m.isValid());
//"Not a valid date"
//false
Update: I made a test harness on JS-Bin with your full sample data. Here is the full working example code using Moment.js. You can specify multiple formats for to try before it will return isValid().
function momentIsDate (dateToCheck) {
return moment(dateToCheck, [
'DD/MM/YYYY',
'YYYY-MM-DDTHH:mm:ss'
]).isValid();
}

They both can be validated with this.
# /^(?:(?:(?:19|20)\d\d[- \/.](?:0[1-9]|1[012])[- \/.](?:0[1-9]|[12][0-9]|3[01])T\d{2}:\d{2}:\d{2})|(?:(?:0[1-9]|1[012])[- \/.](?:0[1-9]|[12][0-9]|3[01])[- \/.](?:19|20)\d{2}))$/
^
(?:
(?:
(?: 19 | 20 )
\d\d [- /.]
(?: 0 [1-9] | 1 [012] )
[- /.]
(?: 0 [1-9] | [12] [0-9] | 3 [01] )
T \d{2} : \d{2} : \d{2}
)
| (?:
(?: 0 [1-9] | 1 [012] )
[- /.]
(?: 0 [1-9] | [12] [0-9] | 3 [01] )
[- /.]
(?: 19 | 20 )
\d{2}
)
)
$

You can actually use the "lenient date" functionality against itself in a pretty cool way to handle this issue. Starting out by using your mm/dd/yyyy example, first make sure that the value matches that format, then, if it does, use the value to create a new Date object:
var checkDateVal = new Date(dateToCheck);
Then, using that new value, rebuild the date string:
var checkDateMonth = checkDateVal.getDate();
var checkDateDay = checkDateVal.getMonth() + 1;
var checkDateYear = checkDateVal.getFullYear();
// force two digits for the day and month, if necessary
checkDateMonth = (checkDateMonth < 10) ? "0" + checkDateMonth : checkDateMonth;
checkDateDay = (checkDateDay < 10) ? "0" + checkDateDay : checkDateDay;
var checkDateString = checkDateMonth + "/" + checkDateDay + "/" + checkDateYear;
Now compare the original date input to the new string value that you created:
if (dateToCheck !== checkDateString) {
// Yell at user for bad data
}
If the date string that was input by the user does not match the date string that was created by the Date object, that means that the object was forced to "massage" the input value to create a real date . . . which means that original input value was an invalid date value to begin with.
And there is your check. :)
The same logic can be applied to the longer date format that you mention . . . I'd recommend using two regex values at the beginning to determine which format the original input is in, and then use that as a flag to drive logic downstream (e.g., how the checkDateString needs to be built to see if the input was valid).

Javascript: Mutating "05/01/2013" into "20130501"?

So I have a string that represents a date and I need to change the format of it. This is what I have so far:
function myFunction()
{
var dateto = "05/01/2013";
dateto.replace("/", "");
//now what?
}
It will always originally be in the MM/DD/YYYY format, and I need to change it to a YYYYMMDD format. I'm looking for something on the lines of dateto = dateto[5..8] + dateto[0..1] + dateto[2..3]
. Not sure how to write that in JS though.

You can use some simple string maniuplation
var dateto = "05/01/2013";
var parts = dateto.split('/');
var newDate = parts[2] + parts[0] + parts[1];
Fiddle: http://jsfiddle.net/kvU6H/

This can be done using replace with a regular expression and capture groups:
"05/01/2013".replace(
/(\d{2})\/(\d{2})\/(\d{4})/, // capture data in groups
"$3$1$2") // replace with captured groups
While the above approach works well enough for this specific case, consider a library like moment.js:
moment
.parse("05/01/2013", "MM/DD/YYY") // parse our format
.format("YYYYMMDD") // write target format

You could consider the substring() function where you just provide the beginning and end positions (or indexes) of the desired string in the original string:
function myFunction()
{
var dateto = "05/01/2013";
return dateto.substring(6, 10) + dateto.substring(0, 2) + dateto.substring(3, 5);
}
returns:
20130501
Indexes start from 0 in Javascript (and most programming languages)... so for your string:
string: 0 5 / 0 1 / 2 0 1 3
index: 0 1 2 3 4 5 6 7 8 9

check input value for specific format using Javascript

I have an input field that allows a user to enter a date.
I need this date to be in the following format: 10Jan13 (capitalization is not important)
There is a popup calender that if used will format the date correctly for the user.
I'd like to check the value of the input onblur using Javascript to be sure that the user did not either paste or type the date improperly.
I am currently checking number-only fields like this:
var numbers = /^[0-9]+$/;
if (!BIDInput.value.match(numbers))
{
checkedInput.value = "";
alert('Not a number');
}
and I'm checking letters-only fields like this:
var letters = /^[a-z]+$/
if (!nameInput.value.match(letters))
{
nameInput.value = "";
alert('Not a letter');
}
I would like to check the date format in a similar a fashion if possible. But anything that accomplishes the task will do. Can anyone point me in the right direction on how to get this done?
I know that client side validation does not replace server side validation. This is for user experience purposes only.

You're pretty much there with what you have. Basically your format is one or two digits, then one of 12 possible strings, followed by two digits. So for instance:
var shortDateRex = /^\d{1,2}(?:Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)\d{2}$/;
Breakdown:
^ Start of string.
\d{1,2} One or two digits.
(:?...) A non-capturing group. Or you could use a capture group if you like.
Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec An alternation, allowing any of those twelve choices. Naturally you can add more if you like. If you have two choices that start the same way (Jan and January, for instance), put the longer one earlier in the alternation.
\d{2} Two digits.
Side note: I'd have to recommend against two-digit dates on principle, and particularly given where in the century we currently are!
Responding to Amberlamps' comment that this doesn't validate the date: Once you've validated the format, it's trivial to then check the date itself if you like (to rule out 30Feb13, for instance):
var validateDateString = (function() {
var monthNames = "Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec".toLowerCase().split("|");
var dateValidateRex = /^(\d{1,2})(Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec)(\d{2})$/i;
var arbitraryCenturyCutoff = 30;
function validateDateString(str) {
var match;
var day, month, year;
var dt;
match = dateValidateRex.exec(str);
if (!match) {
return false;
}
day = parseInt(match[1]);
month = monthNames.indexOf(match[2].toLowerCase()); // You may need a shim on very old browsers for Array#indexOf
year = parseInt(match[3], 10);
year += year > arbitraryCenturyCutoff ? 1900 : 2000;
dt = new Date(year, month, day);
if (dt.getDate() !== day ||
dt.getMonth() !== month ||
dt.getFullYear() !== year) {
// The input was invalid; we know because the date object
// had to adjust something
return false;
}
return true;
}
return validateDateString;
})();
...or something along those lines.
Live Example | Source
Or if (like me) you hate to see a list like that list of month names repeated you can use the RegExp constructor with a string instead, but you have to remember to duplicate your backslashes:
var monthNamesString = "Jan|Feb|Mar|Apr|May|Jun|Jul|Aug|Sep|Oct|Nov|Dec";
var monthNames = monthNamesString.toLowerCase().split("|");
var dateValidateRex = new RegExp("^(\\d{1,2})(" + monthNamesString + ")(\\d{2})$", "i");
Live Example | Source

You would use the following regular expression to check for a string starting with 2 numbers, followed by 3 characters followed by 2 numbers
[0-9]{2}[a-zA-Z]{3}[0-9]{2}

javascript dynamic regex vs hard typed and captures

I've been at this for hours -- I think I need sleep... but no matter how I alter the expression javascript will only capture the 1st and 3rd elements:
var number = 09416;
var mat = "([0-9]+/[0-9]+/[0-9]+\\s+[0-9]+:[0-9]+)\\s+([A-Z]+)\\s+[0-9,]+\\s+(.*?"+number+".+)";
// month / day / year hour : min AMPM byte size filename containing number in middle
var pattern = new RegExp(mat,"gi");
var arr = ['09/07/2010 07:08 PM 1,465,536 BOL09416 BOL31.exe',
'09/06/2010 12:13 PM 110,225 BOL09416_BOL030.exe',
'09/08/2010 04:46 AM 60,564 BOL09416_BOL32.exe',
'09/08/2010 01:08 PM 63,004 bol09416_bol33.exe']
for (var i=0;i<arr.length;i++){
var match = pattern.exec(arr[i]);
alert(match);
}
It is all spaces (no tabs), I've rewriten the regex to be as explainatory as possible... It correctly matches on arr[0] and arr[2], but nulls on the other two.
Tried looking for possible typo's, trying different .+,.*,.+? etc. All online matchers show that it should be working: Example
Anybody have any ideas as to what I'm missing?
====================
Update:
Going through all the awesome suggestions I am stumped even further:
var match = arr[i].match(/([0-9]+\/[0-9]+\/[0-9]+\s+[0-9]+:[0-9]+)\s+([A-Z]+)\s+[0-9,]+\s+(.*?09416.+)/g);
gives match[0] = full string match[1] = undefined. Basically no captures.
where as:
var match = /([0-9]+\/[0-9]+\/[0-9]+\s+[0-9]+:[0-9]+)\s+([A-Z]+)\s+[0-9,]+\s+(.*?09416.+)/g.exec(arr[i]);
DOES return match[0] = full string, match[1] = date, and so on.
So I guess my real question is how to include dynamically made RegExpressions, and have multiple captures? As the only difference between:
var number = "09416";
var mat = "([0-9]+/[0-9]+/[0-9]+\\s+[0-9]+:[0-9]+)\\s+([A-Z]+)\\s+[0-9,]+\\s+(.*?09416.+)";
var pattern = new RegExp(mat,'g');
and
/([0-9]+\/[0-9]+\/[0-9]+\s+[0-9]+:[0-9]+)\s+([A-Z]+)\s+[0-9,]+\s+(.*?09416.+)/g.exec(arr[i]);
is that I hard-typed the number.

var number = 09416;
// month / day / year hour : min AMPM byte size filename containing number in middle
var mat = '^(\d{2}\/\d{2}\/\d{4})\s+(\d{2}:\d{2}\s*[AP]M)\s+((\d+[\d,]?))\s+(.' + number + '.*)$';
var pattern = new RegExp(mat);
var arr = ['09/07/2010 07:08 PM 1,465,536 BOL09416 BOL31.exe',
'09/06/2010 12:13 PM 110,225 BOL09416_BOL030.exe',
'09/08/2010 04:46 AM 60,564 BOL09416_BOL32.exe',
'09/08/2010 01:08 PM 63,004 bol09416_bol33.exe']
for (var i=0;i<arr.length;i++){
var match = arr[i].match(pattern);
console.log(match);
}
Use string.match instead of regex.exec.
Edited
I've removed the global and it worked like it should be. I've also rewritten the regex but it's quite close to yours (not a big deal).
Look at the output by firebug below:
["09/08/2010 04:46 AM ...,564 BOL09416_BOL32.exe", "09/08/2010", "04:46 AM", "60,564", "564", "BOL09416_BOL32.exe"]
0 "09/08/2010 04:46 AM ...,564 BOL09416_BOL32.exe" //whole match
1 "09/08/2010" //date
2 "04:46 AM" //time
3 "60,564" //bytes
4 "564" // last digit of bytes (i can't take this off. but it's harmless)
5 "BOL09416_BOL32.exe" //name of file

I would suggest you try Regexr to build the expression.
try this
([0-9]+/[0-9]+/[0-9]+ +?[0-9]+:[0-9]+) +?([A-Z]+) +?[0-9,]+ +?(.*?09416.*)

Try this regex:
new RegExp('([0-9]+/[0-9]+/[0-9]+\\s+[0-9]+:[0-9]+)\\s+(AM|PM)\\s+([0-9,]+)\\s+([^0-9]*'+number+'.+)','gi')
Time
AM/PM
File size
File name