Question

I want to change the select option selected to another value.
I.e.,

 <select id="myid"> 
<option value="1" selected="selected">1 </option>
<option value="2" >2 </option>
<option value="3" >3 </option>
<option value="4" >4 </option>
</select>

I have to trigger a change in this select and select the 3rd option I have the value how can I do it.?

I am adding an option each time by a function and I want after each addition of the option, I want it to be selected to do further activities.

Answer 1

To change by index

<input type="button" value="Change Select" onclick="changeSelect(3)" />

function changeSelect(x) {
    document.frm.myid.selectedIndex = x-1;
}

to change by value

<input type="button" value="Change Select" onclick="changeSelect1(3)" />

function changeSelect1(x) {
  var myid = document.getElementById('myid');
  var st = myid.options;
  for(var i=0; i<st.length; i++) {
    if(st[i].value == x) {
      myid.selectedIndex = i;
    }
  }
}