Question

我在stackoverflow中找到了这个脚本。

 function showhide(id){
        if (document.getElementById) {
          var divid = document.getElementById(id);
          var divs = document.getElementsByClassName("hideable");
          for(var div in divs) {
             div.style.display = "none";
          }
          divid.style.display = "block";
        } 
        return false;
       }

<a href="#" onclick="showhide('features');" >features</a>
<a href="#" onclick="showhide('design');"  >design</a>
<a href="#" onclick="showhide('create');" >create</a>

<div class="hideable" id="features">Div 1</div>
<div class="hideable" id="design">Div 2</div>
<div class="hideable" id="create">Div 3</div>

但它说，div.style undefined。为什么？ :)

Answer 1

你永远不应该使用for-in循环。

document.getElementsByClassName('someClass')

返回NodeList，它不会从Array.prototype继承，但在某些方面类似。这是一个节点列表，就像名字所说的那样。这意味着它具有length属性，只能使用：

进行访问

var myElements = document.getElementsByClassName('yourClass');
for (var i = 0, ii = myElements.length; i < ii; i++) {
    console.dir(myElements[i].style);
};

以下是你应该如何隐藏元素。

/**
 * Shows or hides an element from the page. Hiding the element is done by
 * setting the display property to "none", removing the element from the
 * rendering hierarchy so it takes up no space. To show the element, the default
 * inherited display property is restored (defined either in stylesheets or by
 * the browser's default style rules.)
 *
 * Caveat 1: if the inherited display property for the element is set to "none"
 * by the stylesheets, that is the property that will be restored by a call to
 * showElement(), effectively toggling the display between "none" and "none".
 *
 * Caveat 2: if the element display style is set inline (by setting either
 * element.style.display or a style attribute in the HTML), a call to
 * showElement will clear that setting and defer to the inherited style in the
 * stylesheet.
 * @param {Element} el Element to show or hide.
 * @param {*} display True to render the element in its default style,
 * false to disable rendering the element.
 */
var showElement = function(el, display) {
  el.style.display = display ? '' : 'none';
};

var myElement = document.getElementById('someID');
showElement(myElement, false);// it should now be hidden.

Answer 2

for(var i = 0; i < divs.length; i++) {
         divs[i].style.display = "none";
      }

编辑：for循环用于循环对象属性

Answer 3

替换

for(var div in divs) {

与

for(var i=0; i<divs.length;i++) {
   var div = divs[i];

divs，getElementsByClassName的结果，实际上不是一个数组，而是一个NodeList，一个类似于数组的对象，你正在迭代它的属性，而不是它的元素。

Answer 4

javascript for（div中的div div）中的

行为不像foreach。在这种情况下，“ div”是索引。因此元素应为：divs [div]

Answer 5

确保for-in循环中的所有元素都是DOM元素。使用for-in：

过滤hasOwnProperty()循环是一种很好的做法

      for(var div in divs) {
           if (divs.hasOwnProperty(div)) {
               if (div && div.style) {
                   div.style.display = "none";
               }
           }
      }

Div风格未定义（Javascript）

5 个答案: