set html as readonly

function set_readonly(obj,bool){
 obj.onbeforeactivate=function() {if(bool) return false}
 obj.onfocus=function (){if(bool) this.blur()}
 obj.onmouseover=function(){if(bool) this.setCapture()}
 obj.onmouseout=function (){if(bool) this.releaseCapture()}
}

 

set_readonly(document.getElementById("span_test"),true)

<span id=span_test>

<select id=test>

<option>1</option>

<option selected>2</option>

<option>3</option>

</select>

</span>