Clever "add tag" javascript help needed

I have this function for adding options to a Select list:

 function addOption(selectbox, value, text, cl )
 {
var optn = document.createElement("OPTION");
optn.text = text;
optn.value = value;
if (cl==1){ optn.className = "nav_option_main"; }
selectbox.options.add(optn);
 }

I have just discovered the "optgroup" tag, but I don't know how to implement it to the drop list.

The function above is called on another selectboxes "OnChange" event, to fill sub-select-box with the desired options.

I don't think it should be too difficult to add the "optgroup" tag into this, or is it?

Thanks and if you need more input let me know...

UPDATE:

When triggering your function Beejamin the optgroup label is 开发者_如何学Gocopied beneath one another. Ex:

 Label
 Label
 Label
   optgroup.1
   optgroup.2
   optgroup.3
   etc...

Thanks for the function though... But how can I fix this?

Here's an example:

http://www.spookandpuff.com/examples/optGroup.html

And here's the function - which is adapted from your original one:

   function addOption(selectbox, contents, cl )
    {

     var addNode = selectbox; //Cache the selectbox, in case we're only adding a single, ungrouped, option.
     if (contents.length > 1) { //If we're adding a group
       addNode = document.createElement("OPTGROUP"); //Set the node to add to to a new optgroup.
       addNode.label = contents[0]; //Use the first label (a string) as the group's label.
       contents.shift(); //Remove the label from the array (so it doesn't get re-used)
     }

      for (var i=0;i < contents.length;i++) {
        var optn = document.createElement("OPTION");
        optn.text = contents[i][0];
        optn.value = contents[i][1];
        if (cl==1){ optn.className = "nav_option_main"; }  
        addNode.appendChild(optn);  //Append this option to either the selectbox, or the group.
      }

     if (contents.length > 1) { //If we've just added a group, we need to add the group to the select box.
       selectbox.appendChild(addNode);
     }

  }

This version accepts a parameter 'contents', rather than a separate params for 'text' and 'value' - this accepts an array of one or more options. So, to add a single option, not as part of a group, do this:

var singleOption = [
    ['singleOption', 1]
  ];

addOption(document.getElementById('selector'), singleOption, 0);

The item in the contents array is itself an array of two items - the text, and the value.

If you stack more than one of these into the contents array, you create an optGroup:

var optionGroup1 = [
    'Group Title',
    ['groupOne.one', 1],
    ['groupOne.two', 2],
    ['groupOne.three', 3],
    ['groupOne.four', 4],
    ['groupOne.five', 5]
  ];

addOption(document.getElementById('selector'), optionGroup1, 0);

The first item is the title for the group, after that, it's just repeating the same content as the single item. When the function detects you're trying to add more than one at a time, it groups them together.

Is that what you're after?

var optgroups = new Array();

function addOptgroup(selectbox, label){

    optgroups[label] = document.createElement("optgroup");
    optgroups[label].label = label;
    selectBox.appendChild(optgroups[label]);

}


 function addOption(selectbox, value, text, cl, optgroupLabel  )
 {
      var optn = document.createElement("OPTION");
      optn.text = text;
      optn.value = value;
      if (cl==1){ optn.className = "nav_option_main"; }

      if(optgroupLabel  ){
          optgroups[optgroupLabel].appendChild(optn);
      }
      else{
          selectbox.appendChild(optn);
      }
 }