javascript date format - vanilla

function formatDate( date, params ) {
    var options = {
        weekday: "short",
        year: "numeric",
        month: "long",
        day: "numeric",
        hour: "2-digit",
        minute: "2-digit",
        timeZone: "UTC",
        timeZoneName: "short",
    };

    if( params ) {
        options = Object.assign( options, params );
    }

    // https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Date/toLocaleString
    return new Date( date ).toLocaleString( 'en-US', options );
}

formatDate( 'Invalid Date String' ); // bad date

formatDate( new Date() );
formatDate( +new Date() ); // timestamp
formatDate( '2016-08-11' ); // Thu, August 11, 2016, 12:00 AM GMT
formatDate( '08/11/2016' );

// 8/11/2016, 7:00 AM
formatDate( '08/11/2016', {
    weekday: undefined,
    month: "numeric",
    timeZoneName: undefined
} );