大神，“+”“-”“*”都算不了？只能算最后一步，这是怎么回事？
<!DOCTYPE html>
<html>
<head>
<title></title>
<script type="text/javascript">
function count(){
var a=document.getElementById('txt1').value;
var b=document.getElementById('txt2').value;
var elect=document.getElementById('select').value;
var result='';
switch("elect"){
case '+':
result = a + b;
break;
case '-':
result=a - b;
break;
case '*':
result=a * b;
break;
default:
result=a / b;
}
document.getElementById("fruit").value=result;
}
</script>
<input type="text " id="txt1"/>
<select id='select'>
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
<input type="text" id="txt2"/>
<input type="button" value=" = " onclick="count()"/ >
<input type="text" id="fruit"/>
</select>
</head>
<body>
</body>
</html>
紫拉2回答
-
刚毅87
你总共有三处错误.var a=document.getElementById('txt1').value;此处 a 获取值为字符串,不能直接进行运算,应该数值化switch("elect") 此处 elect 是变量,不应该加引号,加引号就变为字符串了;case '/': 少了这个判断具体代码如下:<!DOCTYPE html> <html> <head> <title></title> <script type="text/javascript"> function count() { var a = parseInt(document.getElementById('txt1').value); var b = parseInt(document.getElementById('txt2').value); var elect = document.getElementById('select').value; var result ; switch(elect) { case '+': result = a + b; break; case '-': result = a - b; break; case '*': result = a * b; break; case '/': result = a / b; default: result = a / b; } document.getElementById("fruit").value = result; } </script> <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" /> </head> <body> </body> </html>望采纳! -
ahao430
首先， switch("elect"){这里括号里是变量，不要加引号。前面都不匹配，就执行default了，所以一直是除法。其次，result = a + b;这里是字符串，加号进行的是拼接，应该用parseInt，Number，+之类的将a，b转成数值。
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