title: Google Maps - display/hide marker onclick
body: <p>The Problem:
  I got a Google Map.
  In my init() Method I set all the Markers to its lon/lat.
  Now I want to have some checkboxes on my page.
  In my map I have several Markers for Icecream, Playground and Gasstation.
  Now, clicking on the checkbox for Playground I want to display all Playground markers. On disabling the Checkbox, I want to hide all the Playground Markers.
  The same for the other Markers.
  I have created my Checkboxes and written an onclick function for it:</p>
  
  <pre><code>function show_poi_in_map(input_id){
      var select_id = input_id;
      var var_name = $('#' + select_id).attr('checked')?1:0;
      if (var_name == 1) {
          alert('checked');
      }else{
          alert('not checked')
      }
  }
  </code></pre>
  
  <p>But how to go on with it? 
  I am using jQuery. Maybe this will help.</p>