fix column visibility toggle since setting display on cols no longer works

subnets.html

@@ -4,6 +4,16 @@
 <script language="javascript" type="text/javascript">
 <!--
 
+var visibleColumns = {
+  subnet: true,
+  netmask: false,
+  range: true,
+  useable: true,
+  hosts: true,
+  divide: true,
+  join: true,
+};
+
 var curNetwork = 0;
 var curMask = 0;
 
@@ -59,6 +69,12 @@ function startOver()
 
 function recreateTables()
 {
+  // Update header visibility
+  for (const name in visibleColumns) {
+    console.log(name)
+    document.getElementById(name + 'Header').style.display = visibleColumns[name] ? 'table-cell' : 'none';
+  }
+
   var calcbody = document.getElementById('calcbody');
   if (!calcbody) {
     alert('Body not found');
@@ -75,7 +91,7 @@ function recreateTables()
   createRow(calcbody, rootSubnet, curNetwork, curMask, [curMask, rootSubnet[1], rootSubnet], rootSubnet[0]);
 
   document.getElementById('joinHeader').colSpan = (rootSubnet[0] > 0 ? rootSubnet[0] : 1);
-  document.getElementById('col_join').span = (rootSubnet[0] > 0 ? rootSubnet[0] : 1);
+//  document.getElementById('col_join').span = (rootSubnet[0] > 0 ? rootSubnet[0] : 1);
 
   /* Create the bookmark hyperlink */
   var link = document.getElementById('saveLink');
@@ -152,9 +168,11 @@ function createRow(calcbody, node, address, mask, labels, depth)
     calcbody.appendChild(newRow);
 
     /* subnet address */
+    if (visibleColumns.subnet) {
       var newCell = document.createElement('TD');
       newCell.appendChild(document.createTextNode(inet_ntoa(address)+'/'+mask));
       newRow.appendChild(newCell);
+    }
 
     var addressFirst = address;
     var addressLast = subnet_last_address(address, mask);
@@ -182,27 +200,36 @@ function createRow(calcbody, node, address, mask, labels, depth)
     }
 
     /* netmask */
+    if (visibleColumns.netmask) {
       var newCell = document.createElement('TD');
       newCell.appendChild(document.createTextNode(inet_ntoa(subnet_netmask(mask))));
       newRow.appendChild(newCell);
+    }
 
     /* range of addresses */
+    if (visibleColumns.range) {
       var newCell = document.createElement('TD');
       newCell.appendChild(document.createTextNode(addressRange));
       newRow.appendChild(newCell);
+    }
 
     /* useable addresses */
+    if (visibleColumns.useable) {
       var newCell = document.createElement('TD');
       newCell.appendChild(document.createTextNode(useableRange));
       newRow.appendChild(newCell);
+    }
 
     /* Hosts */
+    if (visibleColumns.hosts) {
       var newCell = document.createElement('TD');
       newCell.appendChild(document.createTextNode(numHosts));
       newRow.appendChild(newCell);
+    }
 
     /* actions */
 
+    if (visibleColumns.divide) {
       var newCell = document.createElement('TD');
       newRow.appendChild(newCell);
 
@@ -219,7 +246,9 @@ function createRow(calcbody, node, address, mask, labels, depth)
 	newLink.appendChild(document.createTextNode('Divide'));
 	newCell.appendChild(newLink);
       }
+    }
 
+    if (visibleColumns.join) {
       var colspan = depth - node[0];
 
       for (var i=(labels.length/3)-1; i>=0; i--) {
@@ -248,6 +277,7 @@ function createRow(calcbody, node, address, mask, labels, depth)
 	colspan = 1; // reset for subsequent cells
       }
     }
+  }
 
 }
 
@@ -428,14 +458,18 @@ window.onload = calcOnLoad;
 function toggleColumn(cb)
 {
   var colName = 'col_'+(cb.id.substr(3));
-  var col = document.getElementById(colName);
+//  var col = document.getElementById(colName);
 
-  if (cb.checked) {
-    col.style.display = 'block';
-  }
-  else {
-    col.style.display = 'none';
-  }
+  visibleColumns[cb.id.substr(3)] = cb.checked;
+
+//  if (cb.checked) {
+//    col.style.display = 'table-column';
+//    col.style.visibility = 'visible';
+//  }
+//  else {
+//    col.style.display = 'none';
+//    col.style.visibility = 'collapse';
+//  }
   recreateTables(); /* because IE draws lines all over the place with border-collapse */
 }
 
@@ -458,7 +492,6 @@ P		{
   font-size: 75%;
 }
 
-
 .label {
   font-family: Arial, Verdana, sans-serif;
   font-size: 60%;
@@ -469,7 +502,8 @@ P		{
   font-size: 80%;
   border-collapse: collapse; 
 }
-.calc td {
+
+.calc td, .calc th {
  border: 1px solid black;
 }
 
@@ -541,7 +575,7 @@ If you wish to save this subnetting for later, bookmark <a href="subnets.html" i
 
 </td>
 <td align="right">
-<a href="https://github.com/davidc/subnets"><img alt="Fork me on GitHub" src="https://github.blog/wp-content/uploads/2008/12/forkme_right_white_ffffff.png" style="right: 0;top: 0;position: absolute;" ></a>
+<a href="https://github.com/davidc/subnets"><img alt="Fork me on GitHub" src="https://github.blog/wp-content/uploads/2008/12/forkme_right_white_ffffff.png" style="right: 0;top: 0;position: absolute;"></a>
 </td>
 </tr>
 </table>
@@ -551,24 +585,15 @@ If you wish to save this subnetting for later, bookmark <a href="subnets.html" i
 <br>
 
 <table class="calc" cellspacing="0" cellpadding="2">
-<colgroup>
-<col id="col_subnet">
-<col id="col_netmask" style="display: none">
-<col id="col_range">
-<col id="col_useable">
-<col id="col_hosts">
-<col id="col_divide">
-<col id="col_join">
-</colgroup>
 <thead>
 <tr>
-<td>Subnet address</td>
-<td>Netmask</td>
-<td>Range of addresses</td>
-<td>Useable IPs</td>
-<td>Hosts</td>
-<td>Divide</td>
-<td id="joinHeader">Join</td>
+<th id="subnetHeader">Subnet address</th>
+<th id="netmaskHeader">Netmask</th>
+<th id="rangeHeader">Range of addresses</th>
+<th id="useableHeader">Useable IPs</th>
+<th id="hostsHeader">Hosts</th>
+<th id="divideHeader">Divide</th>
+<th id="joinHeader">Join</th>
 </tr>
 </thead>
 <tbody id="calcbody">