[javascript] Convert JS date time to MySQL datetime

For arbitrary date string,

// Your default date object  
var starttime = new Date();
// Get the iso time (GMT 0 == UTC 0)
var isotime = new Date((new Date(starttime)).toISOString() );
// getTime() is the unix time value, in milliseconds.
// getTimezoneOffset() is UTC time and local time in minutes.
// 60000 = 60*1000 converts getTimezoneOffset() from minutes to milliseconds. 
var fixedtime = new Date(isotime.getTime()-(starttime.getTimezoneOffset()*60000));
// toISOString() is always 24 characters long: YYYY-MM-DDTHH:mm:ss.sssZ.
// .slice(0, 19) removes the last 5 chars, ".sssZ",which is (UTC offset).
// .replace('T', ' ') removes the pad between the date and time.
var formatedMysqlString = fixedtime.toISOString().slice(0, 19).replace('T', ' ');
console.log( formatedMysqlString );

Or a single line solution,

var formatedMysqlString = (new Date ((new Date((new Date(new Date())).toISOString() )).getTime() - ((new Date()).getTimezoneOffset()*60000))).toISOString().slice(0, 19).replace('T', ' ');
console.log( formatedMysqlString );

This solution also works for Node.js when using Timestamp in mysql.

@Gajus Kuizinas's first answer seems to modify mozilla's toISOString prototype