html之获取select的值

<select name="" id="sel-opt">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>

//方法一:
//var oOpt = document.getElementById('sel-opt').value;
//方法二:
var oOpt = document.getElementById('sel-opt');
var oOptVal = oOpt.options[oOpt.selectedIndex].value;
alert(oOptVal);