getElementsByClassName not working [duplicate]

问题

I coded a php page that displays information from a mysql database neatly into tables. I would like to hide empty table rows with an onLoad event handler.

Here is a sample table with code that hides a <td> when it has no content. but i can only get it to work with different IDs:

        <script type="text/javascript">
        function hideTd(id){
            if(document.getElementById(id).textContent == ''){
              document.getElementById(id).style.display = 'none';
            }
          }
        </script>
        </head>
        <body onload="hideTd('1');hideTd('2');hideTd('3');">
        <table border="1">
          <tr>
            <td id="1">not empty</td>
          </tr>
          <tr>
            <td id="2"></td>
          </tr>
          <tr>
            <td id="3"></td>
          </tr>
        </table>
    </body>

what i want to do is use a class for the <td>s to achieve the same thing while only referencing the class once, and not referencing every single id that I want to remove, which will not even work for my dynamic content. I tried using this code:

    <script type="text/javascript">
    function hideTd(){
        if(document.getElementsByClassName().textContent == ''){
          document.getElementsByClassName().style.display = 'none';
        }
      }
    </script>
    </head>
    <body onload="hideTd('1');">
    <table border="1">
      <tr>
        <td class="1">not empty</td>
      </tr>
      <tr>
        <td class="1"></td>
      </tr>
      <tr>
        <td class="1"></td>
      </tr>
    </table>
</body>

but it does not work. its supposed to hide the empty <td>s that have the specified class. how do i hide empty <td>s using classes, not IDs?

回答1:

There are several issues:

Class names (and IDs) are not allowed to start with a digit.
You have to pass a class to getElementsByClassName().
You have to iterate of the result set.

Example (untested):

<script type="text/javascript">
function hideTd(className){
    var elements = document.getElementsByClassName(className);
    for(var i = 0, length = elements.length; i < length; i++) {
       if( elements[i].textContent == ''){
          elements[i].style.display = 'none';
       } 
    }

  }
</script>
</head>
<body onload="hideTd('td');">
<table border="1">
  <tr>
    <td class="td">not empty</td>
  </tr>
  <tr>
    <td class="td"></td>
  </tr>
  <tr>
    <td class="td"></td>
  </tr>
</table>
</body>

Note that getElementsByClassName() is not available up to and including IE8.

Update:

Alternatively you can give the table an ID and use:

var elements = document.getElementById('tableID').getElementsByTagName('td');

to get all td elements.

To hide the parent row, use the parentNode property of the element:

elements[i].parentNode.style.display = "none";

回答2:

If you want to do it by ClassName you could do:

<script type="text/javascript">
function hideTd(className){
    var elements;

    if (document.getElementsByClassName)
    {
        elements = document.getElementsByClassName(className);
    }
    else
    {
        var elArray = [];
        var tmp = document.getElementsByTagName(elements);  
        var regex = new RegExp("(^|\\s)" + className+ "(\\s|$)");
        for ( var i = 0; i < tmp.length; i++ ) {

            if ( regex.test(tmp[i].className) ) {
                elArray.push(tmp[i]);
            }
        }

        elements = elArray;
    }

    for(var i = 0, i < elements.length; i++) {
       if( elements[i].textContent == ''){
          elements[i].style.display = 'none';
       } 
    }

  }
</script>

来源：https://stackoverflow.com/questions/3349332/getelementsbyclassname-not-working

标签

javascript

webforms

html-table

dynamic-data