Changing a <div> class with JavaScript_问答_开发者

I am trying to change the class of certain tags with an onclick() event. The basic premise is to have the background image of each tag change when the user clicks on them, sort of stimulating a "menu selection".

Here is the code I have:

<style type="text/css">

.navCSS0
{
    background-image:url('news_selected.png');
    width:222px;
    height:38px;
}

.navCSS1
{
    width:222px;
    height:38px;
}

.container_news
{
    background-image:url('itsupdates.png');
    height:330px;
    width:965px;
}

.container_left
{
    margin-top:90px;
    margin-left:20px;
    float:left;
    height:auto;
    width:auto;
}

</style>
</header>

<script>
//global arrays to store nav positions, menu options, and the i开发者_如何学编程nfo text
var navid_array = new Array();
navid_array[0] = 'nav1';
navid_array[1] = 'nav2';
navid_array[2] = 'nav3';
navid_array[3] = 'nav4';
navid_array[4] = 'nav5';


//Takes the navid selected, and goes into a loop where the background of the selected menu item is changed to a image
//with rounded corners, while the backgrounds of the other menu items are changed back to light grey or stay the same.
//There is also a call to the change_info() function when the selected menu item has been located.
function nav_color_swap(navid)
  {
    for(var i = 0; i < navid_array.length; i++) {
          if(navid == navid_array[i]) 
            {
                document.getElementById(navid).className = "navCSS0";
            }
          else 
            {
                document.getElementById(navid).className = "navCSS1";
            } 
        }
  }

</script>

<body>
<div class="container_news">
<div class="container_left">
    <div class="navCSS1" id="nav1" onclick="nav_color_swap(this.id)"><a href="#" onclick="nav_color_swap(this.id)">Blah 1</a></div>
    <div class="navCSS1" id="nav2" onclick="nav_color_swap(this.id)"><a href="#" onclick="nav_color_swap(this.id)">Blah 2</a></div>
    <div class="navCSS0" id="nav3" onclick="nav_color_swap(this.id)"><a href="#" onclick="nav_color_swap(this.id)">Blah 3</a></div>
    <div class="navCSS1" id="nav4" onclick="nav_color_swap(this.id)"><a href="#" onclick="nav_color_swap(this.id)">Blah 4</a></div>
    <div class="navCSS1" id="nav5" onclick="nav_color_swap(this.id)"><a href="#" onclick="nav_color_swap(this.id)">Blah 5</a></div>
    </div>
    </div>
</body>
</html>

The problem is, when I run this code, nothing happens... the only one that actually changes is the last menu item ("Blah 5")... any thoughts?

the header tag does now exist, but that's where you put the header of your page, like the navigation. For titles and meta tags, use the head tag.
the only legal children of <html> are <head> and <body>. The sample code has a <script> element that's a child of <html>
nav_color_swap sets the classname for navid, rather than navid_array[i], when navid != navid_array[i]. This is likely the source of your problem.
When that's fixed, the click handlers for the <a> will set the class name for all elements to "navCSS1", since the <a> don't have ID attributes.

Since, at most, two element classes will need to change with each click, I recommend keeping track of the current element rather than looping over all elements:

    <style type="text/css">
    .selected {
        background-image:url('news_selected.png');
    }
    .news, .news li {
        padding: 0;
        margin: 0;
        list-style-type: none;
    }
    ...
    </style>
    <script type="text/javascript">
    function createNavSelector(curr_nav, selectedClass, unselectedClass) {
        return function (nav) {
            curr_nav.className = unselectedClass;
            curr_nav = nav;
            curr_nav.className = selectedClass;
        }
    }
    </script>
    </head>
    <body>
    ...
    <div class="container_news">
      <ul class="news">
        <li id="nav1" onclick="nav_select(this)">Blah 1</li>
        <li id="nav2" onclick="nav_select(this)">Blah 2</li>
        <li id="nav3" class="selected" onclick="nav_select(this)">Blah 3</li>
        <li id="nav4" onclick="nav_select(this)">Blah 4</li>
        <li id="nav5" onclick="nav_select(this)">Blah 5</li>
      </ul>
    </div>
    <script type="text/javascript">
    var nav_select = createNavSelector(document.getElementById('nav3'), 'selected', '');

Since the #nav* appear to be a list of news items or a list of navigation items, I switched to using elements, since they carry more semantic information than <div>s. At this point, div-vs-ol/ul is largely a matter of personal preference.

I also renamed functions and element classes to reflect their purpose, rather than how they fulfill that purpose. That way, you can change their behavior without requiring a change in name.

Did you use the <a> to support old versions of IE? I wouldn't worry about anything older than IE 6.

As per No Refund, No Return's comment, here's some links to get you started on debugging JS using Firebug. Safari also has a good debugger, if that's your browser of choice.

Intro to Firebug
Build Better Pages With Firebug
Guite to JS Debugging using Firebug (video)

A few things with your code:

Your 'head' tags should be <head> </head>, not <header> </header>
Your <script> tag should be inside the <head> element, and it's best practice to specify the language with: <script language="JavaScript" type="text/javascript"> ... </script>
Invoke your code in a function that is triggered at the onload event of the body to be sure the elements your javascript is referencing have actually been initialised on the page

It looks like the problem is this:

Your anchor tag (link) is surrounded by a div (the div itself doesn't take up any more space than the link inside it in this case). When the user clicks the link, its running the onclick of the link (and its passing the id of the link, which is not added as an attribute).

Also, you need to move your script tag into your header (by the way, its "head", not "header")

You could optimize your code in several ways.. a quick solution would be correcting a logical issue in your code

Replace 'navid' in two places with navid_array[i]

document.getElementById(navid_array[i]).className

    if(navid == navid_array[i]) 
        {
            document.getElementById(navid_array[i]).className = "navCSS0";
        }
     else 
        {
            document.getElementById(navid_array[i]).className = "navCSS1";
        }