初学者用一个简单的下拉菜单努力

具体来说，我试图做一个下拉菜单填充链接，当点击时将直接指向谷歌地图中的指定位置。我设法将谷歌地图嵌入到我的页面中，但出于某种原因，我似乎无法得到下降发生，并找不到我的代码中的问题。我也在努力理解如何在下拉菜单中实际创建链接以指向谷歌地图上的选定位置。任何帮助，将不胜感激。该代码我迄今为止...初学者用一个简单的下拉菜单努力

function myFunction() { 
 
    document.getElementById("myDropdown").classList.toggle("show"); 
 
} 
 

 
window.onclick = function(event) { 
 
    if (!event.target.matches('.dropbtn')) { 
 
    var dropdowns = document.getElementByClassName("dropdown-content"); 
 
    var i; 
 
    for (i = 0; i < dropdowns.length; i++) { 
 
     var openDropdown = dropdowns[i]; 
 
     if (openDropdown.classList.contains('show')) { 
 
     openDropdown.classList.remove('show') 
 
     } 
 
    } 
 
    } 
 
} 
 

 
function initMap() { 
 
    var Columbia = { 
 
    lat: 34.006140, 
 
    lng: -81.037532 
 
    }; 
 
    var map = new google.maps.Map(document.getElementById('map'), { 
 
    zoom: 4, 
 
    center: Columbia 
 
    }); 
 
    var marker = new google.maps.Marker({ 
 
    position: Columbia, 
 
    map: map 
 
    }); 
 
}

.dropbtn { 
 
    background-color: #4caf50; 
 
    color: white; 
 
    padding: 16px; 
 
    font-size: 16px; 
 
    border: none; 
 
    cursor: pointer; 
 
} 
 

 
.dropbtn:hover, 
 
.dropbtn:focus { 
 
    background-color: #3e8e41; 
 
} 
 

 
.dropdown { 
 
    position: relative; 
 
    display: inline-block; 
 
} 
 

 
.dropdown-content { 
 
    display: none; 
 
    position: absolute; 
 
    background-color: #f9f9f9; 
 
    min-width: 160px; 
 
    overflow: auto; 
 
    box-shadow: 0px 8px 16px 0px rgba(0, 0, 0, 0.2); 
 
    z-index: 1; 
 
} 
 

 
.dropdown-content a { 
 
    color: black; 
 
    padding: 12px 16px; 
 
    text-decoration: none; 
 
    display: block; 
 
} 
 

 
.dropdown a:hover { 
 
    background-color: #f1f1f1 
 
} 
 

 
#map { 
 
    height: 400px; 
 
    width: 100%; 
 
}

<script async defer src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB5cD8oVYji2MWCAj8JzrAzQtpBy12W30o&callback=initMap"> 
 
</script> 
 
<h3>Google Maps/Form Assignment</h3> 
 
<div id="map"></div> 
 
<div class="dropdown"> 
 
    <button onclick="myFunction()" class="dropbtn">Select a location</button> 
 
    <div id="myDropdown" class="dropdown-content"> 
 
    <a href="#london">London, England</a> 
 
    <a href="#tokyo">Tokyo, Japan</a> 
 
    <a href="#newyork">New York City, USA</a> 
 
    </div> 
 
</div>

来源

2017-03-06 B. Brig

1）class dropdown-conte nt'显示为none，但没有为'show'类定义的样式，因此显示无法显示，2）您在document.getElementByClassName上有语法错误，将其替换为document.getElementsByClassName – nosthertus

我将发布你的解决方案的答案，给我一点时间 – nosthertus

我看到您已经添加2个不同的功能相同的过程中，你只需要1，所以我将显示与修复代码：

<!DOCTYPE html> 
<html> 
<head> 
    <meta charset="utf-8"> 
    <style> 
     .dropbtn { 
      background-color: #4caf50; 
      color: white; 
      padding: 16px; 
      font-size: 16px; 
      border: none; 
      cursor: pointer; 
     } 
     .dropbtn:hover, .dropbtn:focus{ 
      background-color: #3e8e41; 
     } 
     .dropdown{ 
      position: relative; 
      display: inline-block; 
     } 
     .dropdown-content{ 
      display: none; 
      position: absolute; 
      background-color: #f9f9f9; 
      min-width: 160px; 
      overflow: auto; 
      box-shadow: 0px 8px 16px 0px rgba(0,0,0,0.2); 
      z-index: 1; 
     } 
     /*Add this rule so the dropdown can be shown*/ 
     .dropdown-content.show{ 
      display: block; 
     } 
     .dropdown-content a { 
      color: black; 
      padding: 12px 16px; 
      text-decoration: none; 
      display: block; 
     } 
     .dropdown a:hover { 
      background-color: #f1f1f1 
     } 
     #map { 
      height: 400px; 
      width: 100%; 
     } 
    </style> 
</head> 
<body> 
    <h3>Google Maps/Form Assignment</h3> 
    <div id="map"></div> 
    <div class="dropdown"> 
     <button class="dropbtn">Select a location</button> 
     <div id="myDropdown" class="dropdown-content"> 
      <a href="#london">London, England</a> 
      <a href="#tokyo">Tokyo, Japan</a> 
      <a href="#newyork">New York City, USA</a> 
     </div> 
    </div> 

    <script> 
     window.onclick = function(event){ 
      var target = event.target; 

      if(target.matches('.dropbtn')){ 
       var dropdowns = document.getElementsByClassName("dropdown-content"); //This returns a HTMLCollection 

       for(i=0; i < dropdowns.length; i++){ 
        // Since dropdowns is a HTMLCollection, extract the node from the collection 
        var dropdown = dropdowns.item(i); 

        // Toggle the dropdown whenever the button is clicked 
        dropdown.classList.toggle("show"); 
       } 
      } 

      if(target.matches(".dropdown-content > a")){ 
       // Get the location name from the hash 
       var location = target.hash.slice(1); 

       // Extract the location map and set it as center 
       map.setCenter(positions[location]); 
      } 
     }; 
     </script> 
     <script> 
      function initMap() { 
       // Set all locations map 
       window.positions = { 
        london: { 
         lat: 51.5013616, 
         lng: -0.1965444 
        }, 
        southCarolina: { 
         lat: 34.006140, 
         lng: -81.037532 
        } 
       }; 

       window.map = new google.maps.Map(document.getElementById('map'), { 
        zoom: 4, 
        center: positions.southCarolina 
       }); 

       // Add marker positions in the map 
       var markers = { 
        london: new google.maps.Marker({ 
         position: positions.london, 
         map: map 
        }), 
        southCarolina: new google.maps.Marker({ 
         position: positions.southCarolina, 
         map: map 
        }) 
       }; 
      } 

    </script> 
    <script async defer src="https://maps.googleapis.com/maps/api/js?key=AIzaSyB5cD8oVYji2MWCAj8JzrAzQtpBy12W30o&callback=initMap"> 
    </script> 
</body> 
</html>

我在评论中增加了与代码不同之处，应该做些什么。

你需要知道document.getElementsByClassName返回HTMLCollection对象，它不仅具有length财产和方法2这是item和namedItem，你可以看到HTMLCollection的文档和文档的getElementsByClassName

编辑：我有还添加了处理地图位置视图的部分代码，当单击下拉项时，请注意我刚刚为london添加了一个示例，因此您可以继续为其他位置执行其他操作

来源

2017-03-06 04:52:25 nosthertus

初学者用一个简单的下拉菜单努力

回答

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