Java Script как в oper получить значение поля select ?

Question

<html>
 <head>
 <title></title>
 <meta http-equiv="Content-Type" content="text/html; charset=UTF-8">
 <script>
 function res(){
 var a=parseFloat(document.getElementById("a").value);
 var b=parseFloat(document.getElementById("b").value);
 var res=parseFloat(0); 
 var oper=document.getElementById("1").name;

switch (oper){
 case "+":
 res=(a+b)
 break
 case "-":
 res=(a-b)
 break
 case "*":
 res=(a*b)
 break
 case "/":
 res=(a/b)
 default:break; 
 }
 document.getElementById("res").value=res;
 }
 </script>
 
 </head>
 <body>
 <input type="text" id="a">
 <select id="1" >
 <option name="+" >+</option>
 <option name="-" >-</option>
 <option name="*" >*</option>
 <option name="/" >/</option> 
</select>
 <input type="text" id="b">=
 <input type="text" id="res">
 <button onclick="res()">=
 </body>
</html>

Светлана Светова · Accepted Answer

document.getElementById("a").options[0].name
и т. д.