<!DOCTYPE html>
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var a=document.getElementById("txt1").value;
var b=document.getElementById("txt2").value;
var c=document.getElementById("select").value;
var t;
switch(c)
{
case "+":
t=a+b;
break;
case "-":
t=a-b;
break;
case "*":
t=a*b;
break;
default:
t=a/b;
break; }
document.getElementById("fruit").value=t;
}
</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()"/> <!--通过 = 按钮来调用创建的函数,得到结果-->
<input type='text' id="fruit"/>
</body>
</html>
+有可能是字符串拼接 自己改下吧
<html>
<head>
<title> 事件</title>
<script type="text/javascript">
function count(){
var a=document.getElementById("txt1").value;
var b=document.getElementById("txt2").value;
var c=document.getElementById("select").value;
var t;
switch(c)
{
case "+":
t=a+b;
break;
case "-":
t=a-b;
break;
case "*":
t=a*b;
break;
default:
t=a/b;
break; }
document.getElementById("fruit").value=t;
}
</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()"/> <!--通过 = 按钮来调用创建的函数,得到结果-->
<input type='text' id="fruit"/>
</body>
</html>
+有可能是字符串拼接 自己改下吧
function count(){
var a=parseFloat(document.getElementById("txt1").value);
var b=parseFloat(document.getElementById("txt2").value);
var c=document.getElementById("select").value;
var t;
switch(c)
{
case "+":
t=a+b;
break;
case "-":
t=a-b;
break;
case "*":
t=a*b;
break;
default:
t=a/b;
break;
}
document.getElementById("fruit").value=t;
}
t=a+b;
break;
default:
t=a/b;
break;
}
document.getElementById("fruit").value=t;//这句也放错了
}