如何实例调用JS里面的方法？
朋友们好：我对JS不太懂，现在想在可以显示谷歌地图的一个html页面标注小圆圈标记，查找网上有这样的方法，下载了一个JS文件，我如何在我显示地图的div里面调用JS里面的方法，恳请懂的朋友指点一两个方法，谢谢！



下载的这个JS文件是这样的：function GRulerControl() {
  var me = this;
  
  // 可国际化的字符串
  me.RESET_BUTTON_TITLE_ = '清除所有测距标记';
  me.ENABLE_BUTTON_TITLE_ = '添加测距标记已启用，单击这里禁用';
  me.DISABLE_BUTTON_TITLE_ = '添加测距标记已禁用，单击这里启用';
  me.DELETE_BUTTON_TITLE_ = '删除';
  
  me.RESET_BUTTON_IMAGE_ = 'image/ruler_clear.png';
  me.ENABLE_BUTTON_IMAGE_ = 'image/ruler_enabled.png';
  me.DISABLE_BUTTON_IMAGE_ = 'image/ruler_disabled.png';
  me.BACKGROUND_IMAGE_ = 'image/ruler_background.png'
  
  me.KILOMETER_ = '公里';
  me.METER_ = '米';
}

GRulerControl.prototype = new GControl();

/**
 * 初始化标尺控件
 */
GRulerControl.prototype.initialize = function(map) {
  var me = this;
  var container = document.createElement('div');
  me.setButtonStyle_(container);
 
  // “启用/禁用”按钮
  var btnEnable = document.createElement('img');
  btnEnable.width = btnEnable.height = 19;
  GEvent.addDomListener(btnEnable, 'click', 
  function() {
  me.setEnabled(!me.isEnabled());
  me.reset();
  }
  );
  container.appendChild(btnEnable);
  
  // “重置”按钮
  var btnReset = document.createElement('img');
  btnReset.width = btnReset.height = 19;
  btnReset.src = me.RESET_BUTTON_IMAGE_;
  btnReset.title = me.RESET_BUTTON_TITLE_;
  GEvent.addDomListener(btnReset, 'click', 
  function() {
  me.reset();
  }
  );
  container.appendChild(btnReset);
  
  // 距离标签
  var txtInfo = document.createElement('div');
  txtInfo.style.font = 'small Arial';
  txtInfo.style.fontWeight = 'bold';
  txtInfo.style.fontSize = '9pt';
  txtInfo.style.width = '82px';
  container.appendChild(txtInfo);
  
  // 初始化内部变量
  map.rulerControl_ = me;
  me.map_ = map;
  me.head_ = new Object();
  me.tail_ = new Object();
  me.head_.next_ = me.tail_;
  me.tail_.prev_ = me.head_;
  me.btnEnable_ = btnEnable;
  me.btnReset_ = btnReset;
  me.txtInfo_ = txtInfo;
  me.setEnabled(true);
  
  map.getContainer().appendChild(container);
  return container;
}


/**
 * 设置控件的格式
 */
GRulerControl.prototype.setButtonStyle_ = function(button) {
  button.style.backgroundImage = 'url(' + this.BACKGROUND_IMAGE_ + ')';
  button.style.font = 'small Arial';
  button.style.border = '1px solid #888888';
  button.style.padding = '4px';
  button.style.textAlign = 'right';
  button.style.cursor = 'pointer';
}

/**
 * 用恰当的格式表示距离
 */
GRulerControl.prototype.formatDistance_ = function(len) {
  var me = this;
  
  len = Math.round(len);
  if (len <= 1000) {
  return len + ' ' + me.METER_;
  } else if (len <= 1000000) {
  return len / 1000 + ' ' + me.KILOMETER_;
  }
  return Math.round(len / 1000) + ' ' + me.KILOMETER_;
}

/**
 * 格式化角度为字符串
 */
GRulerControl.prototype.formatDegree_ = function(value) {
  value = Math.abs(value);
  var v1 = Math.floor(value);
  var v2 = Math.floor((value - v1) * 60);
  var v3 = Math.round((value - v1) * 3600 % 60);
  return v1 + '°' + v2 + '\'' + v3 + '"';