Just leverage the built-in toISOString method that brings your date to the ISO 8601 format:

let yourDate = new Date()
yourDate.toISOString().split('T')[0]

Where yourDate is your date object.

Edit: @exbuddha wrote this to handle time zone in the comments:

const offset = yourDate.getTimezoneOffset()
yourDate = new Date(yourDate.getTime() - (offset*60*1000))
return yourDate.toISOString().split('T')[0]

I use this way to get the date in format yyyy-mm-dd :)

var todayDate = new Date().toISOString().slice(0, 10);
console.log(todayDate);

2020 ANSWER

You can use the native .toLocaleDateString() function which supports several useful params like locale (to select a format like MM/DD/YYYY or YYYY/MM/DD), timezone (to convert the date) and formats details options (eg: 1 vs 01 vs January).

Examples

const testCases = [
  new Date().toLocaleDateString(), // 8/19/2020
  new Date().toLocaleString(undefined, {year: 'numeric', month: '2-digit', day: '2-digit', weekday:"long", hour: '2-digit', hour12: false, minute:'2-digit', second:'2-digit'}),
  new Date().toLocaleDateString('en-US', {year: 'numeric', month: '2-digit', day: '2-digit'}), // 08/19/2020 (month and day with two digits)
  new Date().toLocaleDateString('en-ZA'), // 2020/08/19 (year/month/day) notice the different locale
  new Date().toLocaleDateString('en-CA'), // 2020-08-19 (year-month-day) notice the different locale
  new Date().toLocaleString("en-US", {timeZone: "America/New_York"}), // 8/19/2020, 9:29:51 AM. (date and time in a specific timezone)
  new Date().toLocaleString("en-US", {hour: '2-digit', hour12: false, timeZone: "America/New_York"}),  // 09 (just the hour)
]

for (const testData of testCases) {
  console.log(testData)
}

Notice that sometimes to output a date in your specific desire format, you have to find a compatible locale with that format. You can find the locale examples here:

Please notice that locale just change the format, if you want to transform a specific date to a specific country or city time equivalent then you need to use the timezone param.

The simplest way to convert your date to the yyyy-mm-dd format, is to do this:

var date = new Date("Sun May 11,2014");
var dateString = new Date(date.getTime() - (date.getTimezoneOffset() * 60000 ))
                    .toISOString()
                    .split("T")[0];

How it works:

• new Date("Sun May 11,2014") converts the string "Sun May 11,2014" to a date object that represents the time Sun May 11 2014 00:00:00 in a timezone based on current locale (host system settings)
• new Date(date.getTime() - (date.getTimezoneOffset() * 60000 )) converts your date to a date object that corresponds with the time Sun May 11 2014 00:00:00 in UTC (standard time) by subtracting the time zone offset
• .toISOString() converts the date object to an ISO 8601 string 2014-05-11T00:00:00.000Z
• .split("T") splits the string to array ["2014-05-11", "00:00:00.000Z"]
• [0] takes the first element of that array

Demo

var date = new Date("Sun May 11,2014");
var dateString = new Date(date.getTime() - (date.getTimezoneOffset() * 60000 ))
                    .toISOString()
                    .split("T")[0];

console.log(dateString);

A combination of some of the answers:

var d = new Date(date);
date = [
  d.getFullYear(),
  ('0' + (d.getMonth() + 1)).slice(-2),
  ('0' + d.getDate()).slice(-2)
].join('-');

format = function date2str(x, y) {
    var z = {
        M: x.getMonth() + 1,
        d: x.getDate(),
        h: x.getHours(),
        m: x.getMinutes(),
        s: x.getSeconds()
    };
    y = y.replace(/(M+|d+|h+|m+|s+)/g, function(v) {
        return ((v.length > 1 ? "0" : "") + z[v.slice(-1)]).slice(-2)
    });

    return y.replace(/(y+)/g, function(v) {
        return x.getFullYear().toString().slice(-v.length)
    });
}

Result:

format(new Date('Sun May 11,2014'), 'yyyy-MM-dd')
"2014-05-11

If you don't have anything against using libraries, you could just use the Moments.js library like so:

var now = new Date();
var dateString = moment(now).format('YYYY-MM-DD');

var dateStringWithTime = moment(now).format('YYYY-MM-DD HH:mm:ss');

<script src=""></script>

You can use toLocaleDateString('fr-CA') on Date object

console.log(new Date('Sun May 11,2014').toLocaleDateString('fr-CA'));

Also I found out that those locales give right result from this locales list List of All Locales and Their Short Codes?

'en-CA'
'fr-CA'
'lt-LT'
'sv-FI'
'sv-SE'

var localesList = ["af-ZA",
  "am-ET",
  "ar-AE",
  "ar-BH",
  "ar-DZ",
  "ar-EG",
  "ar-IQ",
  "ar-JO",
  "ar-KW",
  "ar-LB",
  "ar-LY",
  "ar-MA",
  "arn-CL",
  "ar-OM",
  "ar-QA",
  "ar-SA",
  "ar-SY",
  "ar-TN",
  "ar-YE",
  "as-IN",
  "az-Cyrl-AZ",
  "az-Latn-AZ",
  "ba-RU",
  "be-BY",
  "bg-BG",
  "bn-BD",
  "bn-IN",
  "bo-CN",
  "br-FR",
  "bs-Cyrl-BA",
  "bs-Latn-BA",
  "ca-ES",
  "co-FR",
  "cs-CZ",
  "cy-GB",
  "da-DK",
  "de-AT",
  "de-CH",
  "de-DE",
  "de-LI",
  "de-LU",
  "dsb-DE",
  "dv-MV",
  "el-GR",
  "en-029",
  "en-AU",
  "en-BZ",
  "en-CA",
  "en-GB",
  "en-IE",
  "en-IN",
  "en-JM",
  "en-MY",
  "en-NZ",
  "en-PH",
  "en-SG",
  "en-TT",
  "en-US",
  "en-ZA",
  "en-ZW",
  "es-AR",
  "es-BO",
  "es-CL",
  "es-CO",
  "es-CR",
  "es-DO",
  "es-EC",
  "es-ES",
  "es-GT",
  "es-HN",
  "es-MX",
  "es-NI",
  "es-PA",
  "es-PE",
  "es-PR",
  "es-PY",
  "es-SV",
  "es-US",
  "es-UY",
  "es-VE",
  "et-EE",
  "eu-ES",
  "fa-IR",
  "fi-FI",
  "fil-PH",
  "fo-FO",
  "fr-BE",
  "fr-CA",
  "fr-CH",
  "fr-FR",
  "fr-LU",
  "fr-MC",
  "fy-NL",
  "ga-IE",
  "gd-GB",
  "gl-ES",
  "gsw-FR",
  "gu-IN",
  "ha-Latn-NG",
  "he-IL",
  "hi-IN",
  "hr-BA",
  "hr-HR",
  "hsb-DE",
  "hu-HU",
  "hy-AM",
  "id-ID",
  "ig-NG",
  "ii-CN",
  "is-IS",
  "it-CH",
  "it-IT",
  "iu-Cans-CA",
  "iu-Latn-CA",
  "ja-JP",
  "ka-GE",
  "kk-KZ",
  "kl-GL",
  "km-KH",
  "kn-IN",
  "kok-IN",
  "ko-KR",
  "ky-KG",
  "lb-LU",
  "lo-LA",
  "lt-LT",
  "lv-LV",
  "mi-NZ",
  "mk-MK",
  "ml-IN",
  "mn-MN",
  "mn-Mong-CN",
  "moh-CA",
  "mr-IN",
  "ms-BN",
  "ms-MY",
  "mt-MT",
  "nb-NO",
  "ne-NP",
  "nl-BE",
  "nl-NL",
  "nn-NO",
  "nso-ZA",
  "oc-FR",
  "or-IN",
  "pa-IN",
  "pl-PL",
  "prs-AF",
  "ps-AF",
  "pt-BR",
  "pt-PT",
  "qut-GT",
  "quz-BO",
  "quz-EC",
  "quz-PE",
  "rm-CH",
  "ro-RO",
  "ru-RU",
  "rw-RW",
  "sah-RU",
  "sa-IN",
  "se-FI",
  "se-NO",
  "se-SE",
  "si-LK",
  "sk-SK",
  "sl-SI",
  "sma-NO",
  "sma-SE",
  "smj-NO",
  "smj-SE",
  "smn-FI",
  "sms-FI",
  "sq-AL",
  "sr-Cyrl-BA",
  "sr-Cyrl-CS",
  "sr-Cyrl-ME",
  "sr-Cyrl-RS",
  "sr-Latn-BA",
  "sr-Latn-CS",
  "sr-Latn-ME",
  "sr-Latn-RS",
  "sv-FI",
  "sv-SE",
  "sw-KE",
  "syr-SY",
  "ta-IN",
  "te-IN",
  "tg-Cyrl-TJ",
  "th-TH",
  "tk-TM",
  "tn-ZA",
  "tr-TR",
  "tt-RU",
  "tzm-Latn-DZ",
  "ug-CN",
  "uk-UA",
  "ur-PK",
  "uz-Cyrl-UZ",
  "uz-Latn-UZ",
  "vi-VN",
  "wo-SN",
  "xh-ZA",
  "yo-NG",
  "zh-CN",
  "zh-HK",
  "zh-MO",
  "zh-SG",
  "zh-TW",
  "zu-ZA"
];

localesList.forEach(lcl => {
  if ("2014-05-11" === new Date('Sun May 11,2014').toLocaleDateString(lcl)) {
    console.log(lcl, new Date('Sun May 11,2014').toLocaleDateString(lcl));
  }
});

Simply use this:

var date = new Date('1970-01-01'); // Or your date here
console.log((date.getMonth() + 1) + '/' + date.getDate() + '/' +  date.getFullYear());

Simple and sweet ;)

Shortest

.toJSON().slice(0,10);

var d = new Date('Sun May 11,2014' +' UTC');   // Parse as UTC
let str = d.toJSON().slice(0,10);              // Show as UTC

console.log(str);

toISOString() assumes your date is local time and converts it to UTC. You will get an incorrect date string.

The following method should return what you need.

Date.prototype.yyyymmdd = function() {         

    var yyyy = this.getFullYear().toString();                                    
    var mm = (this.getMonth()+1).toString(); // getMonth() is zero-based         
    var dd  = this.getDate().toString();             

    return yyyy + '-' + (mm[1]?mm:"0"+mm[0]) + '-' + (dd[1]?dd:"0"+dd[0]);
};

Source:

Retrieve year, month, and day, and then put them together. Straight, simple, and accurate.

function formatDate(date) {
    var year = date.getFullYear().toString();
    var month = (date.getMonth() + 101).toString().substring(1);
    var day = (date.getDate() + 100).toString().substring(1);
    return year + "-" + month + "-" + day;
}

//Usage example:
alert(formatDate(new Date()));

The 2021 solution using Intl.

The new Intl Object is now supported on all browsers.
You can choose the format by choosing a "locale" that uses the required format.

The Swedish locale uses the format "yyyy-mm-dd":

// Create a date
const date = new Date(2021, 10, 28);

// Create a formatter using the "sv-SE" locale
const dateFormatter = Intl.DateTimeFormat('sv-SE');

// Use the formatter to format the date
console.log(dateFormatter.format(date)); // "2021-11-28"

Downsides of using Intl:

• You cannot "unformat" or "parse" strings using this method
• You have to search for the required format (for instance on Wikipedia) and cannot use a format-string like "yyyy-mm-dd"

To consider the timezone also, this one-liner should be good without any library:

new Date().toLocaleString("en-IN", {timeZone: "Asia/Kolkata"}).split(',')[0]

You can try this:

npm i timesolver

Use it in your code:

const timeSolver = require('timeSolver');
const date = new Date();
const dateString = timeSolver.getString(date, "YYYY-MM-DD");

You can get the date string by using this method:

getString

new Date().toLocaleDateString('pt-br').split( '/' ).reverse( ).join( '-' );

or

new Date().toISOString().split('T')[0]
new Date('23/03/2020'.split('/').reverse().join('-')).toISOString()
new Date('23/03/2020'.split('/').reverse().join('-')).toISOString().split('T')[0]

Try this!

const formatDate = d => [
    d.getFullYear(),
    (d.getMonth() + 1).toString().padStart(2, '0'),
    d.getDate().toString().padStart(2, '0')
].join('-');

You can make use of padstart.

padStart(n, '0') ensures that a minimum of n characters are in a string and prepends it with '0's until that length is reached.

join('-') concatenates an array, adding '-' symbol between every elements.

getMonth() starts at 0 hence the +1.

I suggest using something like formatDate-js instead of trying to replicate it every time. Just use a library that supports all the major strftime actions.

new Date().format("%Y-%m-%d")

When ES2018 rolls around (works in chrome) you can simply regex it

(new Date())
    .toISOString()
    .replace(
        /^(?<year>\d+)-(?<month>\d+)-(?<day>\d+)T.*$/,
        '$<year>-$<month>-$<day>'
    )

2020-07-14

Or if you'd like something pretty versatile with no libraries whatsoever

(new Date())
    .toISOString()
    .match(
        /^(?<yyyy>\d\d(?<yy>\d\d))-(?<mm>0?(?<m>\d+))-(?<dd>0?(?<d>\d+))T(?<HH>0?(?<H>\d+)):(?<MM>0?(?<M>\d+)):(?<SSS>(?<SS>0?(?<S>\d+))\.\d+)(?<timezone>[A-Z][\dA-Z.-:]*)$/
    )
    .groups

Which results in extracting the following

{
    H: "8"
    HH: "08"
    M: "45"
    MM: "45"
    S: "42"
    SS: "42"
    SSS: "42.855"
    d: "14"
    dd: "14"
    m: "7"
    mm: "07"
    timezone: "Z"
    yy: "20"
    yyyy: "2020"
}

Which you can use like so with replace(..., '$<d>/$<m>/\'$<yy> @ $<H>:$<MM>') as at the top instead of .match(...).groups to get

14/7/'20 @ 8:45

Unfortunately, JavaScript's Date object has many pitfalls. Any solution based on Date's builtin toISOString has to mess with the timezone, as discussed in some other answers to this question. The clean solution to represent an ISO-8601 date (without time) is given by Temporal.PlainDate from the Temporal proposal. As of February 2021, you have to choose the workaround that works best for you.