switch (a)//获取通过下拉框来选择的值来改变加减乘除的运算法则
{
case 0: s = x + y; break;
case 1: s = x - y; break;
ase 2: s = x * y; break;
case 3: s = x / y; break;
}
document.getElementById("fruit").value = s;//设置结果输入框的值
var x = parseInt(document.getElementById("txt1").value);//获取第一个输入框的值
var y = parseInt(document.getElementById("txt2").value);//获取第二个输入框的值
var a = parseInt(document.getElementById("select").selectedIndex);//获取选择框的
var s;
switch(a){
case "+":s=x+y;break;
case "-":s=x-y;break;
case "*":s=x*y;break;
case "/":s=x/y;break;
}
document.getElementById("fruit").value=s;
var x=parseInt(document.getElementById("txt1").value);
var y=parseInt(document.getElementById("txt2").value);
var a=document.getElementById("select").value;
var s=0; 需要先定义s=0,否则会出现undefined的情况
