javascript对select值的简单控制

var selects=document.getElementsByTagName('select');
for(var i=0;i<selects.length;i++){
     selects[i].options[0].text=selects[i].options[2].text;
     selects[i].options[0].value=selects[i].options[2].value;
     selects[i].selectedIndex=0;
}