我在使javascript列表不确定长度时遇到麻烦，仅在分配某些属性时才显示

Question

I have a chatbox and I'm making a block function. I've pretty much got the code but it isn't working (Java isn't my language).

I've got the attribute and I can make it disappear but I cannot do it recursively. In many cases the code stops working altogether.

<table>
<td userclass="" username="cat">cat</td>
<td userclass="" username="hampster">hamster</td>
<td userclass="" username="dog">dog</td>
</table>

<p id="message"></p>

<script>
  var x = document.getElementsByTagName("td");
  var i;
  for (i = 0; i < x.length; i++) {

        var btn = document.getElementsByTagName("td")[i];
        var x = btn.attributes[1].value;

        if (x="hamster")
        {
          document.getElementsByTagName("td")[i].style.visibility = "hidden";
        }else{
          document.getElementsByTagName("td")[i].style.visibility = "visible";}
  }
</script>

Success occurs before I include the 'For' loop Error usually doesn't do anything at all

Answer 1

var defines a variable in the global scope. You are using it to store the list of <td> and the value of an attribute. Try using different variable names first:

var myTds = document.getElementsByTagName("td");
var i;
for (i = 0; i < myTds.length; i++) {
    var btn = myTds[i];
    var x = btn.attributes[1].value;

    if (x=="hamster") {
        myTds[i].style.visibility = "hidden";
    } else {
        myTds[i].style.visibility = "visible";
    }
}

Also note that:

1) You should use == for comparisons;

2) you do not need to use document.getElementsByTagName("td") .

3) Change username="hampster" to username="hamster" in your HTML to see the example working.

JSBin here