Convert date from 'Thu Jun 09 2011 00:00:00 GMT+0530 (India Standard Time)' to 'YYYY-MM-DD' in javascript

You can parse the date using the Date constructor, then spit out the individual time components:

function convert(str) {
  var date = new Date(str),
    mnth = ("0" + (date.getMonth() + 1)).slice(-2),
    day = ("0" + date.getDate()).slice(-2);
  return [date.getFullYear(), mnth, day].join("-");
}

console.log(convert("Thu Jun 09 2011 00:00:00 GMT+0530 (India Standard Time)"))
//-> "2011-06-08"

As you can see from the result though, this will parse the date into the local time zone. If you want to keep the date based on the original time zone, the easiest approach is to split the string and extract the parts you need:

function convert(str) {
  var mnths = {
      Jan: "01",
      Feb: "02",
      Mar: "03",
      Apr: "04",
      May: "05",
      Jun: "06",
      Jul: "07",
      Aug: "08",
      Sep: "09",
      Oct: "10",
      Nov: "11",
      Dec: "12"
    },
    date = str.split(" ");

  return [date[3], mnths[date[1]], date[2]].join("-");
}

console.log(convert("Thu Jun 09 2011 00:00:00 GMT+0530 (India Standard Time)"))
//-> "2011-06-09"

The easiest way for me to convert a date was to stringify it then slice it.

var event = new Date("Fri Apr 05 2019 16:59:00 GMT-0700 (Pacific Daylight Time)");

let date = JSON.stringify(event)
date = date.slice(1,11)

// console.log(date) = '2019-04-05'

function convert(str) {
    var date = new Date(str),
        mnth = ("0" + (date.getMonth()+1)).slice(-2),
        day  = ("0" + date.getDate()).slice(-2);
        hours  = ("0" + date.getHours()).slice(-2);
        minutes = ("0" + date.getMinutes()).slice(-2);
    return [ date.getFullYear(), mnth, day, hours, minutes ].join("-");
}

I used this efficiently in angular because i was losing two hours on updating a $scope.STARTevent, and $scope.ENDevent, IN console.log was fine, however saving to mYsql dropped two hours.

var whatSTART = $scope.STARTevent;
whatSTART = convert(whatever);

THIS WILL ALSO work for END