If you need slightly less control over formatting than the currently accepted answer, Date#toLocaleDateString can be used to create standard locale-specific renderings. The locale and options arguments let applications specify the language whose formatting conventions should be used, and allow some customization of the rendering.

Options key examples:

1. day:
   The representation of the day.
   Possible values are “numeric”, “2-digit”.
2. weekday:
   The representation of the weekday.
   Possible values are “narrow”, “short”, “long”.
3. year:
   The representation of the year.
   Possible values are “numeric”, “2-digit”.
4. month:
   The representation of the month.
   Possible values are “numeric”, “2-digit”, “narrow”, “short”, “long”.
5. hour:
   The representation of the hour.
   Possible values are “numeric”, “2-digit”.
6. minute:
   The representation of the minute.
   Possible values are “numeric”, “2-digit”.
7. second:
   The representation of the second.
   Possible values are “numeric”, 2-digit”.
8. hour12:
   The representation of time format.
   Accepts boolean true or false

All these keys are optional. You can change the number of options values based on your requirements, and this will also reflect the presence of each date time term.

Note: If you would only like to configure the content options, but still use the current locale, passing null for the first parameter will cause an error. Use undefined instead.

For different languages:

1. “en-US”: For American English
2. “en-GB”: For British English
3. “hi-IN”: For Hindi
4. “ja-JP”: For Japanese

You can use more language options.

For example

var options = { weekday: 'long', year: 'numeric', month: 'long', day: 'numeric' };
var today  = new Date();

console.log(today.toLocaleDateString("en-US")); // 9/17/2016
console.log(today.toLocaleDateString("en-US", options)); // Saturday, September 17, 2016
console.log(today.toLocaleDateString("hi-IN", options)); // शनिवार, 17 सितंबर 2016

You can also use the toLocaleString() method for the same purpose. The only difference is this function provides the time when you don’t pass any options.

// Example
9/17/2016, 1:21:34 PM

References:

• toLocaleString()

• toLocaleDateString()

For custom-delimited date formats, you have to pull out the date (or time)
components from a DateTimeFormat object (which is part of the
ECMAScript Internationalization API), and then manually create a string
with the delimiters you want.

To do this, you can use DateTimeFormat#formatToParts. You could
destructure the array, but that is not ideal, as the array output depends on the
locale:

{ // example 1
   let formatter = new Intl.DateTimeFormat('en');
   let example = formatter.formatToParts();
   console.log(example);
}
{ // example 2
   let formatter = new Intl.DateTimeFormat('hi');
   let example = formatter.formatToParts();
   console.log(example);
}

Better would be to map a format array to resultant strings:

function join(date, options, separator) {
   function format(option) {
      let formatter = new Intl.DateTimeFormat('en', option);
      return formatter.format(date);
   }
   return options.map(format).join(separator);
}

let options = [{day: 'numeric'}, {month: 'short'}, {year: 'numeric'}];
let joined = join(new Date, options, '-');
console.log(joined);

You can also pull out the parts of a DateTimeFormat one-by-one using
DateTimeFormat#format, but note that when using this method, as of March
2020, there is a bug in the ECMAScript implementation when it comes to
leading zeros on minutes and seconds (this bug is circumvented by the approach
above).

let date = new Date(2010, 7, 5);
let year = new Intl.DateTimeFormat('en', { year: 'numeric' }).format(date);
let month = new Intl.DateTimeFormat('en', { month: 'short' }).format(date);
let day = new Intl.DateTimeFormat('en', { day: '2-digit' }).format(date);
console.log(`${day}-${month}-${year}`);

When working with dates and times, it is usually worth using a library (eg. luxon, date-fns, moment.js is not recommended for new projects) because of the many hidden complexities of the field.

Note that the ECMAScript Internationalization API, used in the solutions above
is not supported in IE10 (0.03% global browser market share in Feb
2020).

If you need to quickly format your date using plain JavaScript, use getDate, getMonth + 1, getFullYear, getHours and getMinutes:

var d = new Date();

var datestring = d.getDate()  + "-" + (d.getMonth()+1) + "-" + d.getFullYear() + " " +
d.getHours() + ":" + d.getMinutes();

// 16-5-2015 9:50

Or, if you need it to be padded with zeros:

var datestring = ("0" + d.getDate()).slice(-2) + "-" + ("0"+(d.getMonth()+1)).slice(-2) + "-" +
    d.getFullYear() + " " + ("0" + d.getHours()).slice(-2) + ":" + ("0" + d.getMinutes()).slice(-2);

// 16-05-2015 09:50

Use the date.format library:

var dateFormat = require('dateformat');
var now = new Date();
dateFormat(now, "dddd, mmmm dS, yyyy, h:MM:ss TT");

returns:

Saturday, June 9th, 2007, 5:46:21 PM 

dateformat on npm

http://jsfiddle.net/phZr7/1/

Well, what I wanted was to convert today’s date to a MySQL friendly date string like 2012-06-23, and to use that string as a parameter in one of my queries. The simple solution I’ve found is this:

var today = new Date().toISOString().slice(0, 10);

Keep in mind that the above solution does not take into account your timezone offset.

You might consider using this function instead:

function toJSONLocal (date) {
    var local = new Date(date);
    local.setMinutes(date.getMinutes() - date.getTimezoneOffset());
    return local.toJSON().slice(0, 10);
}

This will give you the correct date in case you are executing this code around the start/end of the day.

var date = new Date();

function toLocal(date) {
  var local = new Date(date);
  local.setMinutes(date.getMinutes() - date.getTimezoneOffset());
  return local.toJSON();
}

function toJSONLocal(date) {
  var local = new Date(date);
  local.setMinutes(date.getMinutes() - date.getTimezoneOffset());
  return local.toJSON().slice(0, 10);
}

// check out your devtools console
console.log(date.toJSON());
console.log(date.toISOString());
console.log(toLocal(date));

console.log(toJSONLocal(date));

• Date.toISOString
• Date.toJSON
• String.slice
• External example

Custom formatting function:

For fixed formats, a simple function make the job. The following example generates the international format YYYY-MM-DD:

function dateToYMD(date) {
    var d = date.getDate();
    var m = date.getMonth() + 1; //Month from 0 to 11
    var y = date.getFullYear();
    return '' + y + '-' + (m<=9 ? '0' + m : m) + '-' + (d <= 9 ? '0' + d : d);
}

console.log(dateToYMD(new Date(2017,10,5))); // Nov 5

The OP format may be generated like:

function dateToYMD(date) {
    var strArray=['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec'];
    var d = date.getDate();
    var m = strArray[date.getMonth()];
    var y = date.getFullYear();
    return '' + (d <= 9 ? '0' + d : d) + '-' + m + '-' + y;
}
console.log(dateToYMD(new Date(2017,10,5))); // Nov 5

Note: It is, however, usually not a good idea to extend the JavaScript standard libraries (e.g. by adding this function to the prototype of Date).

A more advanced function could generate configurable output based on a format parameter.

If to write a formatting function is too long, there are plenty of libraries around which does it. Some other answers already enumerate them. But increasing dependencies also has it counter-part.

Standard ECMAScript formatting functions:

Since more recent versions of ECMAScript, the Date class has some specific formatting functions:

toDateString: Implementation dependent, show only the date.

https://262.ecma-international.org/#sec-date.prototype.todatestring

new Date().toDateString(); // e.g. "Fri Nov 11 2016"

toISOString: Show ISO 8601 date and time.

https://262.ecma-international.org/#sec-date.prototype.toisostring

new Date().toISOString(); // e.g. "2016-11-21T08:00:00.000Z"

toJSON: Stringifier for JSON.

https://262.ecma-international.org/#sec-date.prototype.tojson

new Date().toJSON(); // e.g. "2016-11-21T08:00:00.000Z"

toLocaleDateString: Implementation dependent, a date in locale format.

https://262.ecma-international.org/#sec-date.prototype.tolocaledatestring

new Date().toLocaleDateString(); // e.g. "21/11/2016"

toLocaleString: Implementation dependent, a date&time in locale format.

https://262.ecma-international.org/#sec-date.prototype.tolocalestring

new Date().toLocaleString(); // e.g. "21/11/2016, 08:00:00 AM"

toLocaleTimeString: Implementation dependent, a time in locale format.

https://262.ecma-international.org/#sec-date.prototype.tolocaletimestring

new Date().toLocaleTimeString(); // e.g. "08:00:00 AM"

toString: Generic toString for Date.

https://262.ecma-international.org/#sec-date.prototype.tostring

new Date().toString(); // e.g. "Fri Nov 21 2016 08:00:00 GMT+0100 (W. Europe Standard Time)"

Note: it is possible to generate custom output out of those formatting >

new Date().toISOString().slice(0,10); //return YYYY-MM-DD

Examples snippets:

console.log("1) "+  new Date().toDateString());
console.log("2) "+  new Date().toISOString());
console.log("3) "+  new Date().toJSON());
console.log("4) "+  new Date().toLocaleDateString());
console.log("5) "+  new Date().toLocaleString());
console.log("6) "+  new Date().toLocaleTimeString());
console.log("7) "+  new Date().toString());
console.log("8) "+  new Date().toISOString().slice(0,10));

Specifying the locale for standard functions:

Some of the standard functions listed above are dependent on the locale:

• toLocaleDateString()
• toLocaleTimeString()
• toLocalString()

This is because different cultures make uses of different formats, and express their date or time in different ways.
The function by default will return the format configured on the device it runs, but this can be specified by setting the arguments (ECMA-402).

toLocaleDateString([locales[, options]])
toLocaleTimeString([locales[, options]])
toLocaleString([locales[, options]])
//e.g. toLocaleDateString('ko-KR');

The option second parameter, allow for configuring more specific format inside the selected locale. For instance, the month can be show as full-text or abreviation.

toLocaleString('en-GB', { month: 'short' })
toLocaleString('en-GB', { month: 'long' })

Examples snippets:

console.log("1) "+  new Date().toLocaleString('en-US'));
console.log("2) "+  new Date().toLocaleString('ko-KR'));
console.log("3) "+  new Date().toLocaleString('de-CH'));

console.log("4) "+  new Date().toLocaleString('en-GB', { hour12: false }));
console.log("5) "+  new Date().toLocaleString('en-GB', { hour12: true }));

Some good practices regarding locales:

• Most people don’t like their dates to appear in a foreigner format, consequently, keep the default locale whenever possible (over setting ‘en-US’ everywhere).
• Implementing conversion from/to UTC can be challenging (considering DST, time-zone not multiple of 1 hour, etc.). Use a well-tested library when possible.
• Don’t assume the locale correlate to a country: several countries have many of them (Canada, India, etc.)
• Avoid detecting the locale through non-standard ways. Here you can read about the multiple pitfalls: detecting the keyboard layout, detecting the locale by the geographic location, etc..

If you are already using jQuery UI in your project you could do it this way:

var formatted = $.datepicker.formatDate("M d, yy", new Date("2014-07-08T09:02:21.377"));

// formatted will be 'Jul 8, 2014'

Some datepicker date format options to play with are available here.

Note (2022-10): toLocaleFormat has been deprecated for some time and was removed from Firefox as of version 58. See toLocaleFormat

I think you can just use the non-standard Date method toLocaleFormat(formatString)

formatString: A format string in the same format expected by the strftime() function in C.

    var today = new Date();
   today.toLocaleFormat('%d-%b-%Y'); // 30-Dec-2011
    

References:

• toLocaleFormat
• strftime

Plain JavaScript is the best pick for small onetimers.

On the other hand, if you need more date stuff, MomentJS is a great solution.

For example:

moment().format('YYYY-MM-DD HH:m:s');     // now() -> 2015-03-24 14:32:20
moment("20111031", "YYYYMMDD").fromNow(); // 3 years ago
moment("20120620", "YYYYMMDD").fromNow(); // 3 years ago
moment().startOf('day').fromNow();        // 11 hours ago
moment().endOf('day').fromNow();          // in 13 hours

In modern browsers (*), you can just do this:

var today = new Date().toLocaleDateString('en-GB', {
    day : 'numeric',
    month : 'short',
    year : 'numeric'
}).split(' ').join('-');

Output if executed today (january 24ᵗʰ, 2016):

'24-Jan-2016'

(*) According to MDN, “modern browsers” means Chrome 24+, Firefox 29+, Internet Explorer 11, Edge 12+, Opera 15+ & Safari nightly build.

Requested format in one line – no libraries and no Date methods, just regex:

var d = (new Date()).toString().replace(/S+s(S+)s(d+)s(d+)s.*/,'$2-$1-$3');
// date will be formatted as "14-Oct-2015" (pass any date object in place of 'new Date()')

In my testing, this works reliably in the major browsers (Chrome, Safari, Firefox and IE.) As @RobG pointed out, the output of Date.prototype.toString() is implementation-dependent, so for international or non-browser implementations, just test the output to be sure it works right in your JavaScript engine. You can even add some code to test the string output and make sure it’s matching what you expect before you do the regex replace.

Packaged Solution: Luxon or date-fns

If you want to use a one solution to fit all, I recommend using date-fns or Luxon.

Luxon is hosted on the Moment.js website and developed by a Moment.js developer because Moment.js has limitations that the developer wanted to address but couldn’t.

To install:

npm install luxon or yarn add luxon (visit link for other installation methods)

Example:

luxon.DateTime.fromISO('2010-08-10').toFormat('yyyy-LLL-dd');

Yields:

10-Aug-2010

Manual Solution

Using similar formatting as Moment.js, Class DateTimeFormatter (Java), and Class SimpleDateFormat (Java), I implemented a comprehensive solution formatDate(date, patternStr) where the code is easy to read and modify. You can display date, time, AM/PM, etc. See code for more examples.

Example:

formatDate(new Date(), 'EEEE, MMMM d, yyyy HH:mm:ss:S')

(formatDate is implemented in the code snippet below)

Yields:

Friday, October 12, 2018 18:11:23:445

Try the code out by clicking “Run code snippet.”

Date and Time Patterns

yy = 2-digit year; yyyy = full year

M = digit month; MM = 2-digit month; MMM = short month name; MMMM = full month name

EEEE = full weekday name; EEE = short weekday name

d = digit day; dd = 2-digit day

h = hours am/pm; hh = 2-digit hours am/pm; H = hours; HH = 2-digit hours

m = minutes; mm = 2-digit minutes; aaa = AM/PM

s = seconds; ss = 2-digit seconds

S = miliseconds

var monthNames = [
  "January", "February", "March", "April", "May", "June", "July",
  "August", "September", "October", "November", "December"
];
var dayOfWeekNames = [
  "Sunday", "Monday", "Tuesday",
  "Wednesday", "Thursday", "Friday", "Saturday"
];
function formatDate(date, patternStr){
    if (!patternStr) {
        patternStr = 'M/d/yyyy';
    }
    var day = date.getDate(),
        month = date.getMonth(),
        year = date.getFullYear(),
        hour = date.getHours(),
        minute = date.getMinutes(),
        second = date.getSeconds(),
        miliseconds = date.getMilliseconds(),
        h = hour % 12,
        hh = twoDigitPad(h),
        HH = twoDigitPad(hour),
        mm = twoDigitPad(minute),
        ss = twoDigitPad(second),
        aaa = hour < 12 ? 'AM' : 'PM',
        EEEE = dayOfWeekNames[date.getDay()],
        EEE = EEEE.substr(0, 3),
        dd = twoDigitPad(day),
        M = month + 1,
        MM = twoDigitPad(M),
        MMMM = monthNames[month],
        MMM = MMMM.substr(0, 3),
        yyyy = year + "",
        yy = yyyy.substr(2, 2)
    ;
    // checks to see if month name will be used
    patternStr = patternStr
      .replace('hh', hh).replace('h', h)
      .replace('HH', HH).replace('H', hour)
      .replace('mm', mm).replace('m', minute)
      .replace('ss', ss).replace('s', second)
      .replace('S', miliseconds)
      .replace('dd', dd).replace('d', day)
      
      .replace('EEEE', EEEE).replace('EEE', EEE)
      .replace('yyyy', yyyy)
      .replace('yy', yy)
      .replace('aaa', aaa);
    if (patternStr.indexOf('MMM') > -1) {
        patternStr = patternStr
          .replace('MMMM', MMMM)
          .replace('MMM', MMM);
    }
    else {
        patternStr = patternStr
          .replace('MM', MM)
          .replace('M', M);
    }
    return patternStr;
}
function twoDigitPad(num) {
    return num < 10 ? "0" + num : num;
}
console.log(formatDate(new Date()));
console.log(formatDate(new Date(), 'dd-MMM-yyyy')); //OP's request
console.log(formatDate(new Date(), 'EEEE, MMMM d, yyyy HH:mm:ss.S aaa'));
console.log(formatDate(new Date(), 'EEE, MMM d, yyyy HH:mm'));
console.log(formatDate(new Date(), 'yyyy-MM-dd HH:mm:ss.S'));
console.log(formatDate(new Date(), 'M/dd/yyyy h:mmaaa'));

Thank you @Gerry for bringing up Luxon.

@Sébastien — alternative all browser support

new Date(parseInt(496407600)*1000).toLocaleDateString('de-DE', {
year: 'numeric',
month: '2-digit',
day: '2-digit'
}).replace(/./g, '/');

Documentation:
https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleDateString

High-order tagged template literal example based on Date.toLocaleDateString:

const date = new Date(Date.UTC(2020, 4, 2, 3, 23, 16, 738));
const fmt = (dt, lc = "en-US") => (str, ...expr) =>
    str.map((str, i) => str + (expr[i]?dt.toLocaleDateString(lc, expr[i]) :'')).join('')

console.log(fmt(date)`${{year: 'numeric'}}-${{month: '2-digit'}}-${{day: '2-digit'}}`);
// expected output: "2020-05-02"

OK, we have got something called Intl which is very useful for formatting a date in JavaScript these days:

Your date as below:

var date = '10/8/2010';

And you change to Date by using new Date() like below:

date = new Date(date);

And now you can format it any way you like using a list of locales like below:

date = new Intl.DateTimeFormat('en-AU').format(date); // Australian date format: "8/10/2010" 

date = new Intl.DateTimeFormat('en-US').format(date); // USA date format: "10/8/2010" 

date = new Intl.DateTimeFormat('ar-EG').format(date);  // Arabic date format: "٨‏/١٠‏/٢٠١٠"

If you exactly want the format you mentioned above, you can do:

date = new Date(Date.UTC(2010, 7, 10, 0, 0, 0));
var options = {year: "numeric", month: "short", day: "numeric"};
date = new Intl.DateTimeFormat("en-AU", options).format(date).replace(/s/g, '-');

And the result is going to be:

"10-Aug-2010"

For more see the Intl API and Intl.DateTimeFormat documentation.

The Date constructor (and Date.parse()) only accepts one format as a parameter when constructing a date and that is ISO 8601:

// new Date('YYYY-MM-DDTHH:mm:ss.sssZ')
const date = new Date('2017-08-15')

But parsing a from a string is strongly discouraged (MDN recommends against creating date with date strings) due to browser differences and inconsistencies.

The recommended alternative would be building your Date instance directly from the numeric data like this:

new Date(2017, 7, 15) // Month is zero-indexed

That is parsing. Now, to format your date to the string you desire you have several options that are native of the Date object (although I believe none is compliant to the format you require):

date.toString()       // 'Wed Jan 23 2019 17:23:42 GMT+0800 (Singapore Standard Time)'
date.toDateString()   // 'Wed Jan 23 2019'
date.toLocaleString() // '23/01/2019, 17:23:42'
date.toGMTString()    // 'Wed, 23 Jan 2019 09:23:42 GMT'
date.toUTCString()    // 'Wed, 23 Jan 2019 09:23:42 GMT'
date.toISOString()    // '2019-01-23T09:23:42.079Z'

For other formatting options I’m afraid you’ll have to turn to libraries such as Moment.js, day.js and the like.

Credit to Zell Liew from this article for the date formatting tips.

Using an ECMAScript Edition 6 (ES6/ES2015) string template:

let d = new Date();
let formatted = `${d.getFullYear()}-${d.getMonth() + 1}-${d.getDate()}`;

If you need to change the delimiters:

const delimiter = '/';
let formatted = [d.getFullYear(), d.getMonth() + 1, d.getDate()].join(delimiter);

Here’s is some code I just wrote to handle the date formatting for a project I’m working on. It mimics the PHP date formatting functionality to suit my needs. Feel free to use it, it’s just extending the already existing Date() object. This may not be the most elegant solution but it’s working for my needs.

var d = new Date(); 
d_string = d.format("m/d/Y h:i:s");

/**************************************
 * Date class extension
 * 
 */
    // Provide month names
    Date.prototype.getMonthName = function(){
        var month_names = [
                            'January',
                            'February',
                            'March',
                            'April',
                            'May',
                            'June',
                            'July',
                            'August',
                            'September',
                            'October',
                            'November',
                            'December'
                        ];

        return month_names[this.getMonth()];
    }

    // Provide month abbreviation
    Date.prototype.getMonthAbbr = function(){
        var month_abbrs = [
                            'Jan',
                            'Feb',
                            'Mar',
                            'Apr',
                            'May',
                            'Jun',
                            'Jul',
                            'Aug',
                            'Sep',
                            'Oct',
                            'Nov',
                            'Dec'
                        ];

        return month_abbrs[this.getMonth()];
    }

    // Provide full day of week name
    Date.prototype.getDayFull = function(){
        var days_full = [
                            'Sunday',
                            'Monday',
                            'Tuesday',
                            'Wednesday',
                            'Thursday',
                            'Friday',
                            'Saturday'
                        ];
        return days_full[this.getDay()];
    };

    // Provide full day of week name
    Date.prototype.getDayAbbr = function(){
        var days_abbr = [
                            'Sun',
                            'Mon',
                            'Tue',
                            'Wed',
                            'Thur',
                            'Fri',
                            'Sat'
                        ];
        return days_abbr[this.getDay()];
    };

    // Provide the day of year 1-365
    Date.prototype.getDayOfYear = function() {
        var onejan = new Date(this.getFullYear(),0,1);
        return Math.ceil((this - onejan) / 86400000);
    };

    // Provide the day suffix (st,nd,rd,th)
    Date.prototype.getDaySuffix = function() {
        var d = this.getDate();
        var sfx = ["th","st","nd","rd"];
        var val = d%100;

        return (sfx[(val-20)%10] || sfx[val] || sfx[0]);
    };

    // Provide Week of Year
    Date.prototype.getWeekOfYear = function() {
        var onejan = new Date(this.getFullYear(),0,1);
        return Math.ceil((((this - onejan) / 86400000) + onejan.getDay()+1)/7);
    } 

    // Provide if it is a leap year or not
    Date.prototype.isLeapYear = function(){
        var yr = this.getFullYear();

        if ((parseInt(yr)%4) == 0){
            if (parseInt(yr)%100 == 0){
                if (parseInt(yr)%400 != 0){
                    return false;
                }
                if (parseInt(yr)%400 == 0){
                    return true;
                }
            }
            if (parseInt(yr)%100 != 0){
                return true;
            }
        }
        if ((parseInt(yr)%4) != 0){
            return false;
        } 
    };

    // Provide Number of Days in a given month
    Date.prototype.getMonthDayCount = function() {
        var month_day_counts = [
                                    31,
                                    this.isLeapYear() ? 29 : 28,
                                    31,
                                    30,
                                    31,
                                    30,
                                    31,
                                    31,
                                    30,
                                    31,
                                    30,
                                    31
                                ];

        return month_day_counts[this.getMonth()];
    } 

    // format provided date into this.format format
    Date.prototype.format = function(dateFormat){
        // break apart format string into array of characters
        dateFormat = dateFormat.split("");

        var date = this.getDate(),
            month = this.getMonth(),
            hours = this.getHours(),
            minutes = this.getMinutes(),
            seconds = this.getSeconds();
        // get all date properties ( based on PHP date object functionality )
        var date_props = {
            d: date < 10 ? '0'+date : date,
            D: this.getDayAbbr(),
            j: this.getDate(),
            l: this.getDayFull(),
            S: this.getDaySuffix(),
            w: this.getDay(),
            z: this.getDayOfYear(),
            W: this.getWeekOfYear(),
            F: this.getMonthName(),
            m: month < 10 ? '0'+(month+1) : month+1,
            M: this.getMonthAbbr(),
            n: month+1,
            t: this.getMonthDayCount(),
            L: this.isLeapYear() ? '1' : '0',
            Y: this.getFullYear(),
            y: this.getFullYear()+''.substring(2,4),
            a: hours > 12 ? 'pm' : 'am',
            A: hours > 12 ? 'PM' : 'AM',
            g: hours % 12 > 0 ? hours % 12 : 12,
            G: hours > 0 ? hours : "12",
            h: hours % 12 > 0 ? hours % 12 : 12,
            H: hours,
            i: minutes < 10 ? '0' + minutes : minutes,
            s: seconds < 10 ? '0' + seconds : seconds           
        };

        // loop through format array of characters and add matching data else add the format character (:,/, etc.)
        var date_string = "";
        for(var i=0;i<dateFormat.length;i++){
            var f = dateFormat[i];
            if(f.match(/[a-zA-Z]/g)){
                date_string += date_props[f] ? date_props[f] : '';
            } else {
                date_string += f;
            }
        }

        return date_string;
    };
/*
 *
 * END - Date class extension
 * 
 ************************************/

This may help with the problem:

var d = new Date();

var options = {   
    day: 'numeric',
    month: 'long', 
    year: 'numeric'
};

console.log(d.toLocaleDateString('en-ZA', options));

A JavaScript solution without using any external libraries:

var now = new Date()
months = ['Jan', 'Feb', 'Mar', 'Apr', 'May', 'Jun', 'Jul', 'Aug', 'Sep', 'Oct', 'Nov', 'Dec']
var formattedDate = now.getDate() + "-" + months[now.getMonth()] + "-" + now.getFullYear()
alert(formattedDate)

TypeScript version

It can be easily enhanced to support any format string desired. When a generic solution like this is so easy to create, and date formatting comes up so often in applications, I wouldn’t recommend hard-coding date format code all over your application. It’s harder to read and hides your intentions. Format strings show your intentions clearly.

Prototype functions

interface Date {
    format(formatString: string): string;
}

Date.prototype.format = function (formatString: string): string {
  return Object.entries({
    YYYY: this.getFullYear(),
    YY: this.getFullYear().toString().substring(2),
    yyyy: this.getFullYear(),
    yy: this.getFullYear().toString().substring(2),
    MMMM: this.toLocaleString('default', { month: 'long' }),
    MMM: this.toLocaleString('default', { month: 'short' }),
    MM: (this.getMonth() + 1).toString().padStart(2, '0'),
    M: this.getMonth() + 1,
    DDDD: this.toLocaleDateString('default', { weekday: 'long' }),
    DDD: this.toLocaleDateString('default', { weekday: 'short' }),
    DD: this.getDate().toString().padStart(2, '0'),
    D: this.getDate(),
    dddd: this.toLocaleDateString('default', { weekday: 'long' }),
    ddd: this.toLocaleDateString('default', { weekday: 'short' }),
    dd: this.getDate().toString().padStart(2, '0'),
    d: this.getDate(),
    HH: this.getHours().toString().padStart(2, '0'), // military
    H: this.getHours().toString(), // military
    hh: (this.getHours() % 12).toString().padStart(2, '0'),
    h: (this.getHours() % 12).toString(),
    mm: this.getMinutes().toString().padStart(2, '0'),
    m: this.getMinutes(),
    SS: this.getSeconds().toString().padStart(2, '0'),
    S: this.getSeconds(),
    ss: this.getSeconds().toString().padStart(2, '0'),
    s: this.getSeconds(),
    TTT: this.getMilliseconds().toString().padStart(3, '0'),
    ttt: this.getMilliseconds().toString().padStart(3, '0'),
    AMPM: this.getHours() < 13 ? 'AM' : 'PM',
    ampm: this.getHours() < 13 ? 'am' : 'pm',
  }).reduce((acc, entry) => {
    return acc.replace(entry[0], entry[1].toString())
  }, formatString)
}

Demo

function unitTest() {
    var d: Date = new Date()
    console.log(d.format('MM/dd/yyyy hh:mm:ss')) // 12/14/2022 03:38:31
    console.log(d.format('yyyy-MM-dd HH:mm:ss')) // 2022-12-14 15:38:31
}

unitTest()

JavaScript version

It’s the same. Just remove the interface, and the type names after the colons and their associated colons.

Snippet

Date.prototype.format = function(formatString) {
  return Object.entries({
    YYYY: this.getFullYear(),
    YY: this.getFullYear().toString().substring(2),
    yyyy: this.getFullYear(),
    yy: this.getFullYear().toString().substring(2),
    MMMM: this.toLocaleString('default', { month: 'long'  }),
    MMM: this.toLocaleString('default',  { month: 'short' }),
    MM: (this.getMonth() + 1).toString().padStart(2, '0'),
    M: this.getMonth() + 1,
    DDDD: this.toLocaleDateString('default', { weekday: 'long'  }),
    DDD: this.toLocaleDateString('default',  { weekday: 'short' }),
    DD: this.getDate().toString().padStart(2, '0'),
    D: this.getDate(),
    dddd: this.toLocaleDateString('default', { weekday: 'long'  }),
    ddd: this.toLocaleDateString('default',  { weekday: 'short' }),
    dd: this.getDate().toString().padStart(2, '0'),
    d: this.getDate(),
    HH: this.getHours().toString().padStart(2, '0'), // military
    H: this.getHours().toString(), // military
    hh: (this.getHours() % 12).toString().padStart(2, '0'),
    h: (this.getHours() % 12).toString(),
    mm: this.getMinutes().toString().padStart(2, '0'),
    m: this.getMinutes(),
    SS: this.getSeconds().toString().padStart(2, '0'),
    S: this.getSeconds(),
    ss: this.getSeconds().toString().padStart(2, '0'),
    s: this.getSeconds(),
    TTT: this.getMilliseconds().toString().padStart(3, '0'),
    ttt: this.getMilliseconds().toString().padStart(3, '0'),
    AMPM: this.getHours() < 13 ? 'AM' : 'PM',
    ampm: this.getHours() < 13 ? 'am' : 'pm',
  }).reduce((acc, entry) => {
    return acc.replace(entry[0], entry[1].toString())
  }, formatString)
}



function unitTest() {
  var d = new Date()
  console.log(d.format('MM/dd/yyyy hh:mm:ss')) // 12/14/2022 03:38:31
  console.log(d.format('yyyy-MM-dd HH:mm:ss')) // 2022-12-14 15:38:31
}

unitTest()

A useful and flexible way for formatting the DateTimes in JavaScript is Intl.DateTimeFormat:

var date = new Date();
var options = { year: 'numeric', month: 'short', day: '2-digit'};
var _resultDate = new Intl.DateTimeFormat('en-GB', options).format(date);
// The _resultDate is: "12 Oct 2017"
// Replace all spaces with - and then log it.
console.log(_resultDate.replace(/ /g,'-'));

Result Is: "12-Oct-2017"

The date and time formats can be customized using the options argument.

The Intl.DateTimeFormat object is a constructor for objects that enable language sensitive date and time formatting.

Syntax

new Intl.DateTimeFormat([locales[, options]])
Intl.DateTimeFormat.call(this[, locales[, options]])

Parameters

locales

Optional. A string with a BCP 47 language tag, or an array of such strings. For the general form and interpretation of the locales argument, see the Intl page. The following Unicode extension keys are allowed:

nu
Numbering system. Possible values include: "arab", "arabext", "bali", "beng", "deva", "fullwide", "gujr", "guru", "hanidec", "khmr", "knda", "laoo", "latn", "limb", "mlym", "mong", "mymr", "orya", "tamldec", "telu", "thai", "tibt".
ca
Calendar. Possible values include: "buddhist", "chinese", "coptic", "ethioaa", "ethiopic", "gregory", "hebrew", "indian", "islamic", "islamicc", "iso8601", "japanese", "persian", "roc".

Options

Optional. An object with some or all of the following properties:

localeMatcher

The locale matching algorithm to use. Possible values are "lookup" and "best fit"; the default is "best fit". For information about this option, see the Intl page.

timeZone

The time zone to use. The only value implementations must recognize is "UTC"; the default is the runtime’s default time zone. Implementations may also recognize the time zone names of the IANA time zone database, such as "Asia/Shanghai", "Asia/Kolkata", "America/New_York".

hour12

Whether to use 12-hour time (as opposed to 24-hour time). Possible values are true and false; the default is locale dependent.

formatMatcher

The format matching algorithm to use. Possible values are "basic" and "best fit"; the default is "best fit". See the following paragraphs for information about the use of this property.

The following properties describe the date-time components to use in formatted output and their desired representations. Implementations are required to support at least the following subsets:

weekday, year, month, day, hour, minute, second
weekday, year, month, day
year, month, day
year, month
month, day
hour, minute, second
hour, minute

Implementations may support other subsets, and requests will be negotiated against all available subset-representation combinations to find the best match. Two algorithms are available for this negotiation and selected by the formatMatcher property: A fully specified "basic" algorithm and an implementation dependent “best fit” algorithm.

weekday

The representation of the weekday. Possible values are "narrow", "short", "long".

era

The representation of the era. Possible values are "narrow", "short", "long".

year

The representation of the year. Possible values are "numeric", "2-digit".

month

The representation of the month. Possible values are "numeric", "2-digit", "narrow", "short", "long".

day

The representation of the day. Possible values are "numeric", "2-digit".

hour

The representation of the hour. Possible values are "numeric", "2-digit".

minute

The representation of the minute. Possible values are "numeric", "2-digit".

second

The representation of the second. Possible values are "numeric", "2-digit".

timeZoneName

The representation of the time zone name. Possible values are "short", "long".
The default value for each date-time component property is undefined, but if all component properties are undefined, then the year, month and day are assumed to be "numeric".

Check Online

More Details

new Date().toLocaleDateString()

// "3/21/2018"

More documentation at developer.mozilla.org

We have lots of solutions for this, but I think the best of them is Moment.js. So I personally suggest to use Moment.js for date and time operations.

console.log(moment().format('DD-MMM-YYYY'));

<script src="//cdnjs.cloudflare.com/ajax/libs/moment.js/2.14.1/moment.min.js"></script>

If you are using jQuery UI in your code, there is an inbuilt function called formatDate(). I am using it this way to format today’s date:

var testdate = Date();
testdate = $.datepicker.formatDate( "d-M-yy",new Date(testdate));
alert(testdate);

You can see many other examples of formatting date in the jQuery UI documentation.

This is how I implemented for my npm plugins

var monthNames = [
  "January", "February", "March",
  "April", "May", "June", "July",
  "August", "September", "October",
  "November", "December"
];

var Days = [
  "Sunday", "Monday", "Tuesday", "Wednesday",
  "Thursday", "Friday", "Saturday"
];

var formatDate = function(dt,format){
  format = format.replace('ss', pad(dt.getSeconds(),2));
  format = format.replace('s', dt.getSeconds());
  format = format.replace('dd', pad(dt.getDate(),2));
  format = format.replace('d', dt.getDate());
  format = format.replace('mm', pad(dt.getMinutes(),2));
  format = format.replace('m', dt.getMinutes());
  format = format.replace('MMMM', monthNames[dt.getMonth()]);
  format = format.replace('MMM', monthNames[dt.getMonth()].substring(0,3));
  format = format.replace('MM', pad(dt.getMonth()+1,2));
  format = format.replace(/M(?![ao])/, dt.getMonth()+1);
  format = format.replace('DD', Days[dt.getDay()]);
  format = format.replace(/D(?!e)/, Days[dt.getDay()].substring(0,3));
  format = format.replace('yyyy', dt.getFullYear());
  format = format.replace('YYYY', dt.getFullYear());
  format = format.replace('yy', (dt.getFullYear()+"").substring(2));
  format = format.replace('YY', (dt.getFullYear()+"").substring(2));
  format = format.replace('HH', pad(dt.getHours(),2));
  format = format.replace('H', dt.getHours());
  return format;
}

pad = function(n, width, z) {
  z = z || '0';
  n = n + '';
  return n.length >= width ? n : new Array(width - n.length + 1).join(z) + n;
}

You should have a look at DayJs It’s a remake of momentJs but modular architecture oriented so lighter.

Fast 2kB alternative to Moment.js with the same modern API

Day.js is a minimalist JavaScript library that parses, validates, manipulates, and displays dates and times for modern browsers with a largely Moment.js-compatible API. If you use Moment.js, you already know how to use Day.js.

var date = Date.now();
const formatedDate = dayjs(date).format("YYYY-MM-DD")
console.log(formatedDate);

<script src="https://cdnjs.cloudflare.com/ajax/libs/dayjs/1.8.16/dayjs.min.js" crossorigin="anonymous"></script>

Inspired by JD Smith’s marvellous regular expression solution, I suddenly had this head-splitting idea:

var D = Date().toString().split(" ");
console.log(D[2] + "-" + D[1] + "-" + D[3]);

var today = new Date();
var formattedToday = today.toLocaleDateString() + ' ' + today.toLocaleTimeString();

For any one looking for a really simple ES6 solution to copy, paste and adopt:

const dateToString = d => `${d.getFullYear()}-${('00' + (d.getMonth() + 1)).slice(-2)}-${('00' + d.getDate()).slice(-2)}` 

// how to use:
const myDate = new Date(Date.parse('04 Dec 1995 00:12:00 GMT'))
console.log(dateToString(myDate)) // 1995-12-04

As of 2019, it looks like you can get toLocaleDateString to return only certain parts and then you can join them as you wish:

var date = new Date();

console.log(date.toLocaleDateString("en-US", { day: 'numeric' }) 
            + "-"+ date.toLocaleDateString("en-US", { month: 'short' })
            + "-" + date.toLocaleDateString("en-US", { year: 'numeric' }) );

> 16-Nov-2019

console.log(date.toLocaleDateString("en-US", { month: 'long' }) 
            + " " + date.toLocaleDateString("en-US", { day: 'numeric' }) 
            + ", " + date.toLocaleDateString("en-US", { year: 'numeric' }) );

> November 16, 2019