为什么少了return sum 会显示不出来
function app2(x,y)
{ var sum,x,y;
sum = x * y;
return sum;
}
var req1=app2(5,6);
var req2=app2(2,3);
var sumq=req1+req2;
document.write("req1的值:"+req1+"<br/>");
document.write("req2的值:"+req2+"<br/>");
document.write(req1+"与"+req2+"和:"+sumq);
