Develop Reference

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}

How to append an extra 'Zero' after decimal in Javascript

Hye,
Iam new to javascript working with one textbox validation for decimal numbers . Example format should be 66,00 .but if user type 66,0 and dont type two zero after comma then after leaving text box it should automatically append to it .so that it would be correct format of it . How can i get this .How can i append ?? here is my code snippet.
function check2(sender){
var error = false;
var regex = '^[0-9][0-9],[0-9][0-9]$';
var v = $(sender).val();
var index = v.indexOf(',');
var characterToTest = v.charAt(index + 1);
var nextCharAfterComma = v.charAt(index + 2);
if (characterToTest == '0') {
//here need to add
}
}

Use .toFixed(2)
Read this article: http://www.javascriptkit.com/javatutors/formatnumber.shtml
|EDIT| This will also fix the issue if a user types in too many decimals. Better to do it this way, rather than having a if to check each digit after the comma.

.toFixed() converts a number to string and if you try to convert it to a float like 10.00
then it is impossible.
Example-
10.toFixed(2) // "10.00" string
parseFloat("10.00") // 10
Number("10.00") // 10

How do I get the unicode/hex representation of a symbol out of the HTML using JavaScript/jQuery?

Say I have an element like this...
<math xmlns="http://www.w3.org/1998/Math/MathML">
<mo class="symbol">α</mo>
</math>
Is there a way to get the unicode/hex value of alpha α, &#x03B1, using JavaScript/jQuery? Something like...
$('.symbol').text().unicode(); // I know unicode() doesn't exist
$('.symbol').text().hex(); // I know hex() doesn't exist
I need &#x03B1 instead of α and it seems like anytime I insert &#x03B1 into the DOM and try to retrieve it right away, it gets rendered and I can't get &#x03B1 back; I just get α.

Using mostly plain JavaScript, you should be able to do:
function entityForSymbolInContainer(selector) {
var code = $(selector).text().charCodeAt(0);
var codeHex = code.toString(16).toUpperCase();
while (codeHex.length < 4) {
codeHex = "0" + codeHex;
}
return "&#x" + codeHex + ";";
}
Here's an example: http://jsfiddle.net/btWur/

charCodeAt will get you the decimal value of the string:
"α".charCodeAt(0); //returns 945
0x03b1 === 945; //returns true
toString will then get the hex string
(945).toString(16); // returns "3b1"
(Confirmed to work in IE9 and Chrome)

If you would try to convert Unicode character out of BMP (basic multilingual plane) in ways above - you are up for a nasty surprise. Characters out of BMP are encoded as multiple UTF16 values for example:
"🔒".length = 2 (one part for shackle one part for lock base :) )
so "🔒".charCodeAt(0) will give you 55357 which is only 'half' of number while "🔒".charCodeAt(1) will give you 56594 which is the other half.
To get char codes for those values you might wanna use use following string extension function
String.prototype.charCodeUTF32 = function(){
return ((((this.charCodeAt(0)-0xD800)*0x400) + (this.charCodeAt(1)-0xDC00) + 0x10000));
};
you can also use it like this
"&#x"+("🔒".charCodeUTF32()).toString(16)+";"
to get html hex codes.
Hope this saves you some time.

for example in case you need to convert this hex code to unicode
e68891e4bda0e4bb96
pick two character time by time ,
if the dec ascii code is over 127 , add a % before
return url decode string
function hex2a(hex) {
var str = '';
for (var i = 0; i < hex.length; i += 2){
var dec = parseInt(hex.substr(i, 2), 16);
character = String.fromCharCode(dec);
if (dec > 127)
character = "%"+hex.substr(i,2);
str += character;
}
return decodeURI(str);
}

Javascript date regex DD/MM/YYYY

I know there are a lot of regex threads out there by I need a specific pattern I couldn't fin anywhere
This regex validates in a YYYY-MM-DD format
/^\d{4}[\/\-](0?[1-9]|1[012])[\/\-](0?[1-9]|[12][0-9]|3[01])$/
I need the pattern to be DD/MM/YYYY
(day first since it's in spanish and only "/", "-" should not be allowed)
I searched several regex libraries and I think this one should work... but since I'm not familiar with regex I'm not sure it validates like that
(0[1-9]|[12][0-9]|3[01])[ \.-](0[1-9]|1[012])[ \.-](19|20|)\d\d
I also don't know ho to escape the slashes, I try to "see" the logic in the string but it's like trying "see" the Matrix code for me. I'm placing the regex string in a options .js
[...] },
"date": {
"regex": (0[1-9]|[12][0-9]|3[01])[ \.-](0[1-9]|1[012])[ \.-](19|20|)\d\d,
"alertText": "Alert text AAAA-MM-DD"
},
"other type..."[...]
So, if the regex is ok, how would I escape it?
if it's not, what's the correct regex and how do I escape it? :P
Thanks a lot

You could take the regex that validates YYYY/MM/DD and flip it around to get what you need for DD/MM/YYYY:
/^(0?[1-9]|[12][0-9]|3[01])[\/\-](0?[1-9]|1[012])[\/\-]\d{4}$/
BTW - this regex validates for either DD/MM/YYYY or DD-MM-YYYY
P.S. This will allow dates such as 31/02/4899

A regex is good for matching the general format but I think you should move parsing to the Date class, e.g.:
function parseDate(str) {
var m = str.match(/^(\d{1,2})\/(\d{1,2})\/(\d{4})$/);
return (m) ? new Date(m[3], m[2]-1, m[1]) : null;
}
Now you can use this function to check for valid dates; however, if you need to actually validate without rolling (e.g. "31/2/2010" doesn't automatically roll to "3/3/2010") then you've got another problem.
[Edit] If you also want to validate without rolling then you could add a check to compare against the original string to make sure it is the same date:
function parseDate(str) {
var m = str.match(/^(\d{1,2})\/(\d{1,2})\/(\d{4})$/)
, d = (m) ? new Date(m[3], m[2]-1, m[1]) : null
, nonRolling = (d&&(str==[d.getDate(),d.getMonth()+1,d.getFullYear()].join('/')));
return (nonRolling) ? d : null;
}
[Edit2] If you want to match against zero-padded dates (e.g. "08/08/2013") then you could do something like this:
function parseDate(str) {
function pad(x){return (((''+x).length==2) ? '' : '0') + x; }
var m = str.match(/^(\d{1,2})\/(\d{1,2})\/(\d{4})$/)
, d = (m) ? new Date(m[3], m[2]-1, m[1]) : null
, matchesPadded = (d&&(str==[pad(d.getDate()),pad(d.getMonth()+1),d.getFullYear()].join('/')))
, matchesNonPadded = (d&&(str==[d.getDate(),d.getMonth()+1,d.getFullYear()].join('/')));
return (matchesPadded || matchesNonPadded) ? d : null;
}
However, it will still fail for inconsistently padded dates (e.g. "8/08/2013").

Take a look from here https://www.regextester.com/?fam=114662
Use this following Regular Expression Details, This will support leap year also.
var reg = /^(((0[1-9]|[12]\d|3[01])\/(0[13578]|1[02])\/((19|[2-9]\d)\d{2}))|((0[1-9]|[12]\d|30)\/(0[13456789]|1[012])\/((19|[2-9]\d)\d{2}))|((0[1-9]|1\d|2[0-8])\/02\/((19|[2-9]\d)\d{2}))|(29\/02\/((1[6-9]|[2-9]\d)(0[48]|[2468][048]|[13579][26])|(([1][26]|[2468][048]|[3579][26])00))))$/g;
Example

Scape slashes is simply use \ before / and it will be escaped. (\/=> /).
Otherwise you're regex DD/MM/YYYY could be next:
/^[0-9]{2}[\/]{1}[0-9]{2}[\/]{1}[0-9]{4}$/g
Explanation:
[0-9]: Just Numbers
{2} or {4}: Length 2 or 4. You could do {2,4} as well to length between two numbers (2 and 4 in this case)
[\/]: Character /
g : Global -- Or m: Multiline (Optional, see your requirements)
$: Anchor to end of string. (Optional, see your requirements)
^: Start of string. (Optional, see your requirements)
An example of use:
var regex = /^[0-9]{2}[\/][0-9]{2}[\/][0-9]{4}$/g;
var dates = ["2009-10-09", "2009.10.09", "2009/10/09", "200910-09", "1990/10/09",
"2016/0/09", "2017/10/09", "2016/09/09", "20/09/2016", "21/09/2016", "22/09/2016",
"23/09/2016", "19/09/2016", "18/09/2016", "25/09/2016", "21/09/2018"];
//Iterate array
dates.forEach(
function(date){
console.log(date + " matches with regex?");
console.log(regex.test(date));
});
Of course you can use as boolean:
if(regex.test(date)){
//do something
}

I use this function for dd/mm/yyyy format :
// (new Date()).fromString("3/9/2013") : 3 of september
// (new Date()).fromString("3/9/2013", false) : 9 of march
Date.prototype.fromString = function(str, ddmmyyyy) {
var m = str.match(/(\d+)(-|\/)(\d+)(?:-|\/)(?:(\d+)\s+(\d+):(\d+)(?::(\d+))?(?:\.(\d+))?)?/);
if(m[2] == "/"){
if(ddmmyyyy === false)
return new Date(+m[4], +m[1] - 1, +m[3], m[5] ? +m[5] : 0, m[6] ? +m[6] : 0, m[7] ? +m[7] : 0, m[8] ? +m[8] * 100 : 0);
return new Date(+m[4], +m[3] - 1, +m[1], m[5] ? +m[5] : 0, m[6] ? +m[6] : 0, m[7] ? +m[7] : 0, m[8] ? +m[8] * 100 : 0);
}
return new Date(+m[1], +m[3] - 1, +m[4], m[5] ? +m[5] : 0, m[6] ? +m[6] : 0, m[7] ? +m[7] : 0, m[8] ? +m[8] * 100 : 0);
}

Try using this..
[0-9]{2}[/][0-9]{2}[/][0-9]{4}$
this should work with this pattern DD/DD/DDDD where D is any digit (0-9)

((?=\d{4})\d{4}|(?=[a-zA-Z]{3})[a-zA-Z]{3}|\d{2})((?=\/)\/|\-)((?=[0-9]{2})[0-9]{2}|(?=[0-9]{1,2})[0-9]{1,2}|[a-zA-Z]{3})((?=\/)\/|\-)((?=[0-9]{4})[0-9]{4}|(?=[0-9]{2})[0-9]{2}|[a-zA-Z]{3})
Regex Compile on it
2012/22/Jan
2012/22/12
2012/22/12
2012/22/12
2012/22/12
2012/22/12
2012/22/12
2012-Dec-22
2012-12-22
23/12/2012
23/12/2012
Dec-22-2012
12-2-2012
23-12-2012
23-12-2012

If you are in Javascript already, couldn't you just use Date.Parse() to validate a date instead of using regEx.
RegEx for date is actually unwieldy and hard to get right especially with leap years and all.

For people who needs to validate years earlier than year 1900, following should do the trick. Actually this is same as the above answer given by [#OammieR][1] BUT with years including 1800 - 1899.
/^(((0[1-9]|[12]\d|3[01])\/(0[13578]|1[02])\/((19|[2-9]\d)\d{2}))|((0[1-9]|[12]\d|3[01])\/(0[13578]|1[02])\/((18|[2-9]\d)\d{2}))|((0[1-9]|[12]\d|30)\/(0[13456789]|1[012])\/((19|[2-9]\d)\d{2}))|((0[1-9]|[12]\d|30)\/(0[13456789]|1[012])\/((18|[2-9]\d)\d{2}))|((0[1-9]|1\d|2[0-8])\/02\/((19|[2-9]\d)\d{2}))|(29\/02\/((1[6-9]|[2-9]\d)(0[48]|[2468][048]|[13579][26])|((16|[2468][048]|[3579][26])00))))$/
Hope this helps someone who needs to validate years earlier than 1900, such as 01/01/1855, etc.
Thanks #OammieR for the initial idea.

Do the following change to the jquery.validationengine-en.js file and update the dd/mm/yyyy inline validation by including leap year:
"date": {
// Check if date is valid by leap year
"func": function (field) {
//var pattern = new RegExp(/^(\d{4})[\/\-\.](0?[1-9]|1[012])[\/\-\.](0?[1-9]|[12][0-9]|3[01])$/);
var pattern = new RegExp(/^(0?[1-9]|[12][0-9]|3[01])[\/\-\.](0?[1-9]|1[012])[\/\-\.](\d{4})$/);
var match = pattern.exec(field.val());
if (match == null)
return false;
//var year = match[1];
//var month = match[2]*1;
//var day = match[3]*1;
var year = match[3];
var month = match[2]*1;
var day = match[1]*1;
var date = new Date(year, month - 1, day); // because months starts from 0.
return (date.getFullYear() == year && date.getMonth() == (month - 1) && date.getDate() == day);
},
"alertText": "* Invalid date, must be in DD-MM-YYYY format"

I build this regular to check month 30/31 and let february to 29.
new RegExp(/^((0[1-9]|[12][0-9]|3[01])(\/)(0[13578]|1[02]))|((0[1-9]|[12][0-9])(\/)(02))|((0[1-9]|[12][0-9]|3[0])(\/)(0[469]|11))(\/)\d{4}$/)
I think, it's more simple and more flexible and enough full.
Perhaps first part can be contract but I Don't find properly.

This validates date like dd-mm-yyyy
([0-2][0-9]|(3)[0-1])(\-)(((0)[0-9])|((1)[0-2]))(\-)([0-9][0-9][0-9][0-9])
This can use with javascript like angular reactive forms

It can be done like this for dd/mm/yyyy:
^(3[01]|[12][0-9]|0[1-9])/(1[0-2]|0[1-9])/[0-9]{4}$
For mm/dd/yy, mm/dd/yyyy, dd/mm/yy, and dd/mm/yyyy:
Allowing leading zeros to be omitted:
^[0-3]?[0-9]/[0-3]?[0-9]/(?:[0-9]{2})?[0-9]{2}$
Requiring leading zeros:
^[0-3][0-9]/[0-3][0-9]/(?:[0-9][0-9])?[0-9][0-9]$
For more details: https://www.oreilly.com/library/view/regular-expressions-cookbook/9781449327453/ch04s04.html