                        课程
                    
                        /前端开发
                        
                            /JavaScript
                        
                        /JavaScript进阶篇

完整代码各位酌情参考

<!DOCTYPE html>

<html>

<head>

function count(){

var result;

var txt1=document.getElementById("txt1").value;

num1=parseInt(txt1);

//获取第一个输入框的值

var txt2=document.getElementById("txt2").value;

num2=parseInt(txt2);

//获取第二个输入框的值

var count=document.getElementById("select").value;

//获取选择框的值

switch(count){

case "+": result=num1+num2;break;

case "-": result=num1-num2;break;

case "*": result=num1*num2;break;

case "/": result=num1/num2;break;

}

//获取通过下拉框来选择的值来改变加减乘除的运算法则

//设置结果输入框的值

document.getElementById("fruit").value=result;

return result;

}

</script>

</head>

<body>

</select>

</body>

</html>

慕粉4169323

2016-10-19

源自：JavaScript进阶篇 6-11

关注问题我要回答

1051

操作

收起

3 回答

冒牌小冬瓜
2016-10-26

function count()

{

var a = document.getElementById("txt1").value;

var num1 = parseInt(a);

var b = document.getElementById("txt2").value;

var num2 = parseInt(b);

var c = document.getElementById("select").value;

var d;

if(c == "+")

{

d = num1 + num2;

}

else if(c == "-")

{

d = num1 - num2;

}

else if(c == "*")

{

d = num1 * num2;

}

else

{

d = num1 / num2;

}

document.getElementById("fruit").value = d;

return d;

}

0 回复有任何疑惑可以回复我~

收起回答

慕粉3790335
2016-10-19

<!DOCTYPE html>
<html>
<head>
<meta http-equiv="Content-Type" content="text/html" charset="utf-8">
<title> 事件</title>
<script type="text/javascript">
   function count(){

    //获取第一个输入框的值
    var x = document.getElementById('txt1').value;
    //获取第二个输入框的值
var y = document.getElementById('txt2').value;
//获取选择框的值
var symbol = document.getElementById('select').value;
//获取通过下拉框来选择的值来改变加减乘除的运算法则
if (document.getElementById('select').value=="+")
{
  var result = Number(x) + Number(y);
}
else if (document.getElementById('select').value=="-")
{
  var result = x - y;
}
else if (document.getElementById('select').value=="*")
{
  var result = x * y;
}
else
{
  if(y!=0) {var result = x / y;}
  else {alert("除数不能为0！");}

}
    //设置结果输入框的值
    document.getElementById('fruit').value = result;
   }
</script>
</head>
<body>
   <input type='text' id='txt1' />
   <select id='select'>
  <option value='+'>+</option>
  <option value="-">-</option>
  <option value="*">*</option>
  <option value="/">/</option>
   </select>
   <input type='text' id='txt2' />
   <input type='button' value=' = ' onclick="count()" /> 
   <input type='text' id='fruit' />
</body>
</html>