title: What is the difference between "marker.setVisible(false)" and "marker.setMap(null)" in Google Maps v3?
body: <p>I want to clear a marker on Google Maps.</p>
  
  <p>What is the difference between <code>marker.setVisible(false)</code> and <code>marker.setMap(null)</code>?</p>
  
  <p>But I don't know, which is right?</p>