title: Change zoom with html tag event
body: <p>i'am a beginner in GMaps API and javascript, so this should be an easy question for you that are really experts. I have started to "play around" with the API, and wanted to try a simple thing, but I couldn't make it! I have look around for the answer, but I didn't get it. I have created the map:</p>
  
  <pre><code>&lt;script type="text/javascript"&gt;
  function initialize() {
  
      //CREATE THE MAP
      var mapOptions = {
        center: new google.maps.LatLng(-35.8190,-61.9010),
        zoom: 15,
        mapTypeId: google.maps.MapTypeId.SATELLITE
      };
      var map = new google.maps.Map(document.getElementById("map_canvas"),
          mapOptions);
  
      //GET THE ZOOM
      var ez = map.getZoom();
  
      //TRYING TO CHANGE ZOOM FROM EXTERNAL LINK (DOESN'T WORK)
  function cambiarZOOM(nro) {
      var newZ = ez + nro;
      map.setZoom(newZ);
      }
  
  }
  google.maps.event.addDomListener(window, 'load', initialize);
  
  &lt;/script&gt;
  </code></pre>
  
  <p>Now, the HTML:</p>
  
  <pre><code>&lt;html&gt;&lt;body onload="initialize()"&gt;
  &lt;input type="button" onclick="cambiarZOOM(5)" value="CAMBIAR ZOOM"&gt;
  &lt;/body&gt;&lt;/html&gt;
  </code></pre>
  
  <p>Well, now I'am reading about google.maps.trigger(); but I'm not getting it. I will apreciate  a lot your answer!. THANK YOU!</p>