[SuperZen]

selectedIndex находится в options

<select name="imodel" id="imodelphone" onchange="func1()">
    <option value="5">iPhone 5</option>
    <option value="6">iPhone 6</option>
 </select>
 
<script>
  console.log( {
    imodelphone: document.getElementById('imodelphone'),
    opts: document.getElementById('imodelphone').options,
    selected: document.getElementById('imodelphone').options[document.getElementById('imodelphone').options.selectedIndex].value
  })
</script>