Question

In javascript you can create a Date object from a string, like

var mydate = new Date('2008/05/10 12:08:20');
console.log(mydate); //=> Sat May 10 2008 12:08:20 GMT+0200

Now try this using milliseconds in the string

var mydate = new Date('2008/05/10 12:08:20:551'); // or '2008/05/10 12:08:20.551'
console.log(mydate); //=> NaN

Just out of curiosity: why is this?

EDIT: thanks for your answers, which all offer sufficient explanation. Maybe in some future there will be support for use of milliseconds in date strings. Untill then I cooked up this, which may be of use to somebody:

function dateFromStringWithMilliSeconds(datestr){
    var dat = datestr.split(' ')
        ,timepart = dat[1].split(/:|\./)
        ,datestr = dat[0]+' '+timepart.slice(0,3).join(':')
        ,ms = timepart[timepart.length-1] || 0
        ,date;
    date = new Date(datestr);
    date.setMilliseconds(ms);
    return date;
}

Answer 1

dateString

String value representing a date. The string should be in a format recognized by the parse method (IETF-compliant RFC 1123 timestamps).

This format doesn’t seem to accommodate milliseconds in the date… It may be best to just define the date without ms and then call setMilliseconds() afterwards.