Add HTML control(s) via javascript

Question

Something is eluding me ... it seems obvious, but I can't quite figure it out.

I want to add/remove a couple of HTML controls to a page (plain old html) when a user changes value of a dropdown list. An example is to add or remove a "number of guests in this room" textbox for each (of a number) of rooms requested ...

So if a user selects:

1 room, there is one text box

2 rooms, there are two text boxes

3 rooms, three text boxes

back to 2 rooms, two text boxes

and so on ...

Answer 1

Using straight DOM and Javascript you would want to modify the InnterHtml property of a DOM object which will contain the text boxes...most likely a div. So it would look something like:

var container = document.getElementById("myContainerDiv");
var html;
for(var i = 0; i < selectedRooms; i++)
{
    html = html + "<input type=text ... /><br />";
}
container.innerHtml = html;

Using a Javascript library like jQuery could make things slightly easier:

var html;
for(var i = 0; i < selectedRooms; i++)
{
    html = html + "<input type=text ... /><br />";
}

$("#myContainerDiv").append(html);

Answer 2

for your select list of rooms, add an onchange event handler that will show/hide the text boses.

<script>
  //swap $ with applicable lib call (if avail)
  function $(id){
    return document.getElementById(id);
  }
  function adjustTexts(obj){
    var roomTotal = 4;
    var count = obj.selectedIndex;
    //show/hide unrequired text boxes...
    for(var i=0;i<roomTotal;i++){
      if(i < count){
        $('room'+ (i+1)).style.display = 'block';
      } else {
        $('room'+ (i+1)).style.display = 'none';
      }
    }
  }
</script>


<select name="rooms" onchange="adjustTexts(this);">
  <option>1</option>
  <option>2</option>
  <option>3</option>
  <option>4</option>
</select>

<div id="room1">
  <label>Room 1</label>:<input type="text" name="room1text"/>
</div>

<div id="room2" style="display:none;">
  <label>Room 2</label>:<input type="text" name="room2text"/>
</div>

<div id="room3" style="display:none;">
  <label>Room 3</label>:<input type="text" name="room3text"/>
</div>

<div id="room4" style="display:none;">
  <label>Room 4</label>:<input type="text" name="room4text"/>
</div>

Answer 3

given HTML:

<select name="rooms" id="rooms">
  <option value="1">1 room</option>
  <option value="2">2 rooms</option>
  <option value="3">3 rooms</option>
</select>
<div id="boxes"></div>

javascript:

document.getElementById('rooms').onchange = function() {
  var e = document.getElementById('boxes');
  var count = parseInt(document.getElementById('rooms').value);
  e.innerHTML = '';

  for(i = 1; i <= count; i++) {
    e.innerHTML += 'Room '+i+' <input type="text" name="room'+i+'" /><br />';
  } 
}