谷歌地图api3错误

问题描述：

我试图在网页中嵌入带有标记的Google地图。但是，如果我使用以下代码，则会收到未定义的警报消息。

I am trying to embed a google map with markers in my webpage. But I am getting an undefined alert message if I use the following code

var infowindow = null;
var geocoder;
$(document).ready(function () { initialize();  });

function codeAddress(address) {
    geocoder = new google.maps.Geocoder();
    geocoder.geocode( { 'address': address}, function(results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
            //alert(results[0].geometry.location);
            return (results[0].geometry.location);
        } 
    });
}

function initialize() {
    default_location = codeAddress("<?php echo $location;?>");
    alert(default_location);
}

取而代之如果我在codeAdress函数中使用alert它正确显示了经度和纬度。

Instead of that If i am doing the alert with in the codeAdress function as below it is correctly showing the latitude and longitude.

var infowindow = null;
var geocoder;
$(document).ready(function () { initialize();  });

function codeAddress(address) {
    geocoder = new google.maps.Geocoder();
    geocoder.geocode( { 'address': address}, function(results, status) {
        if (status == google.maps.GeocoderStatus.OK) {
            alert(results[0].geometry.location);

        } 
    });
}

function initialize() {
    codeAddress("<?php echo $location;?>");
}

有人可以识别出什么问题吗？我是JavaScript新手

Can somebody Identify whats the problem? I am new to javascripts

答

geocoder调用是异步的，这意味着它需要一些时间才能返回并且不遵循顺序订单如书面。这也意味着在第一个位中，函数在到达 return（results [0] .geometry.location）语句之前结束。所以 alert 没有任何显示。

The geocoder call is asynchronous, meaning that it takes some time to return and does not follow the sequential order as written. It also means that in the first bit, the function finishes before it gets to your return (results[0].geometry.location) statement. So alert has nothing to display.

除了在 geocode request，你可以编写一个回调模式来分离脚本逻辑。当 geocode 调用成功时，执行传递位置作为参数的回调。

Other than inserting statements inside the geocode request, you can write a callback pattern to separate the script logic. The callback, which passes the location as the parameter, executes when the geocode call is successful.

http://jsfiddle.net/3KXKm/

  var infowindow = null;
  var geocoder = new google.maps.Geocoder();

  $(document).ready(function () { initialize();  });

  function codeAddress(address, callback) {
    geocoder.geocode( { 'address': address}, function(results, status) {
      if (status == google.maps.GeocoderStatus.OK) {
        callback(results[0].geometry.location);
      } 
    });
  }

  function initialize() {
    codeAddress("Chicago, IL", function(default_location) {
      var map = new google.maps.Map(document.getElementById("map_canvas"),
        { center: default_location,
        zoom: 3, mapTypeId: google.maps.MapTypeId.ROADMAP });

      locations = ["Los Angeles", "Davis", "Truth or Consequences",
        "Ann Arbor", "Massachusetts"];

      for (var i = 0; i < locations.length; i++) {
        codeAddress(locations[i], function(latLng) {
          new google.maps.Marker({map:map, position:latLng});
        });
      }
    });
  }

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