js change option selected code example
Example 1: make select option selected javascript
document.getElementById('personlist').getElementsByTagName('option')[11].selected = 'selected'
Example 2: js select option in form
<form name="AddAndEdit">
<select name="list" id="personlist">
<option value="P1">Person1</option>
<option value="P2">Person2</option>
<option value="P3">Person3</option>
</select>
</form>