function TextualZoomControl() {
}
TextualZoomControl.prototype = new GControl();

TextualZoomControl.prototype.initialize = function(map) {
  var container = document.createElement("div");
  var zoomInDiv = document.createElement("div");
  this.setButtonStyle_(zoomInDiv);
  container.appendChild(zoomInDiv);
  zoomInDiv.appendChild(document.createTextNode("+"));
  GEvent.addDomListener(zoomInDiv, "click", function() {
    map.zoomIn();
  });

  var zoomOutDiv = document.createElement("div");
  this.setButtonStyle_(zoomOutDiv);
  container.appendChild(zoomOutDiv);
  zoomOutDiv.appendChild(document.createTextNode("-"));
  GEvent.addDomListener(zoomOutDiv, "click", function() {
    map.zoomOut();
  });

  map.getContainer().appendChild(container);
  return container;
}
TextualZoomControl.prototype.getDefaultPosition = function() {
  return new GControlPosition(G_ANCHOR_TOP_LEFT, new GSize(7, 7));
}
TextualZoomControl.prototype.setButtonStyle_ = function(button) {
  button.style.color = "#FFF";
  button.style.backgroundColor = "#333";
  button.style.font = "small Arial";
  button.style.padding = "1px";
  button.style.marginBottom = "3px";
  button.style.textAlign = "center";
  button.style.width = "2em";
  button.style.cursor = "pointer";
}
var map = new GMap2(document.getElementById("map"));
map.addControl(new TextualZoomControl());
map.setCenter(new GLatLng(37.441944, -122.141944), 13);