Javascript date format ( YYYY-MM_DD)

 function formatDate(date) {

    var d = new Date(date),

        month = '' + (d.getMonth() + 1),

        day = '' + d.getDate(),

        year = d.getFullYear();

    if (month.length < 2) month = '0' + month;

    if (day.length < 2) day = '0' + day;

    return [year, month, day].join('-');

}

document.getElementById('res').innerHTML =  formatDate('Sun May 11,2014') ;