Add and Remove Search Marker and Show Info Window on Google Maps API

I am building a page with Google Maps JavaScript V3 API. I have this function that searches an address and then adds a marker:

function codeAddress() {
    var address = document.getElementById('address').value;
      geocoder.geocode( { 'address': address}, function(results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
            map.setCenter(results[0].geometry.location);
            var marker = new google.maps.Marker({
              map: map,
              position: results[0].geometry.location
            });
            marker.setIcon('http://maps.google.com/mapfiles/arrow.png');
            content = "test";
            infowindow.setContent(content);
            infowindow.open(map, marker);
        } else {
          alert('Your search was not successful for the following reason: ' + status);
        }
    });
}

Currently, when you search once it works as it should but when I search again I would like to remove the first marker that is placed and only show the marker for the current search address. Also how can I make it show an info window for the current search address?