JavaScript 实现当前地理位置定位功能

<!DOCTYPE html>
<html lang="en">
<head>
  <meta charset="UTF-8">
  <meta name="viewport" content="width=device-width, initial-scale=1.0,maximum-scale=1.0,user-scalable=no">
  <title>Title</title>
</head>
<body>
您目前在<p></p>
</body>
<script>
  //定义一个空的位置构造函数
  function Location(){};
  //定义一个可以获得经纬度的方法
  Location.prototype.getLocation = function(callback){
    var options = {
      enableHighAccuracy: true,
      maximumAge: 1000
    };
    this.callback = Object.prototype.toString.call(callback) =="[object Function]" ?
        callback :
        function(address){
          alert(address.province + address.city);
          console.log("getocation(callbackFunction) 可获得定位信息对象");
        };
    var self = this;
    if (navigator.geolocation) {
      //浏览器支持geolocation
      navigator.geolocation.getCurrentPosition(function(position){
        //经度
        var longitude = position.coords.longitude;
        //纬度
        var latitude = position.coords.latitude;
        self.loadMapApi(longitude,latitude);
      }, self.onError, options);
    } else {
      //浏览器不支持geolocation
    }
  };
  //定义一个可以解析经纬度的方法，调用百度的api
  Location.prototype.loadMapApi = function(longitude, latitude){
    var self = this;
    var oHead = document.getElementsByTagName('HEAD').item(0);
    var oScript= document.createElement("script");
    oScript.type = "text/javascript";
    oScript.src="http://api.map.baidu.com/getscript?v=2.0&amp;ak=A396783ee700cfdb9ba1df281ce36862&amp;services=&amp;t=20140930184510";
    oHead.appendChild(oScript);
    oScript.onload = function(date){
      var point = new BMap.Point(longitude, latitude);
      var gc = new BMap.Geocoder();
      gc.getLocation(point, function(rs) {
        var addComp = rs.addressComponents;
        self.callback(addComp);
      });
    }
  };
  //定义出现查询位置出现意外的方法
  Location.prototype.onError = function(error) {
    switch (error.code) {
      case 1:
        alert("位置服务被拒绝");
        break;
      case 2:
        alert("暂时获取不到位置信息");
        break;
      case 3:
        alert("获取信息超时");
        break;
      case 4:
        alert("未知错误");
        break;
    }
  };
  //调用
  var local = new Location();
  local.getLocation(function(res){
    var str=""
    for(i in res ){
      str=res[i]+str
    }
    document.querySelector("p").innerHTML=str;
  })
</script>
</html>