Div风格未定义(Javascript)

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')

返回一个NodeList,它不从中继承Array.prototype,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.这意味着它有一个length属性,只能使用以下方法访问:

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

这是你应该如何隐藏一个元素.

/**
 * 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

确保for-in循环中的所有元素都是 DOM 元素。使用以下方式过滤for-in循环是一个很好的做法hasOwnProperty()：

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