![[Web front-end] Node.js quick start](https://img.php.cn/upload/course/000/000/067/662b5d34ba7c0227.png)
Correction status：qualified
Teacher's comments：
Collection
Collection
代码：
<!DOCTYPE html>
<html>
<meta charset="utf-8">
<head>
<title>3.迷你计算器</title>
</head>
<body>
<input type="text" name="one" id="one" placeholder="第一个数字">
<select name="js" id="js">
<option value="kong">符号</option>
<option value="jia">+</option>
<option value="jian">-</option>
<option value="cheng">*</option>
<option value="chu">/</option>
</select>
<input type="text" name="two" id="two" placeholder="第二个数字">
<input type="submit" name="submit" id="submit" value="计算" onclick="jisuan();">
<p>结果：<span id="jg"></span></p>
<script type="text/javascript">
function jisuan(){
var one = document.getElementById('one')
var two = document.getElementById('two')
var js = document.getElementById('js')
var jg = document.getElementById('jg')
if(one.value.length == 0){
jg.innerHTML = '请输入第一个数字'
return false
}else if(isNaN(one.value)){
jg.innerHTML = '非法数字'
return false
}else if(two.value.length == 0){
jg.innerHTML = '请输入第二个数字'
return false
}else if(isNaN(two.value)){
jg.innerHTML = '非法数字'
return false
}else{
var one = parseFloat(one.value)
var two = parseFloat(two.value)
}
switch(js.value){
case 'kong':
jg.innerHTML = '请选择操作类型'
break
case 'jia':
jg.innerHTML = one + two
break
case 'jian':
jg.innerHTML = one - two
break
case 'cheng':
jg.innerHTML = one * two
break
case 'chu':
if(two==0){
jg.innerHTML = '除数不能为零'
return false
}
jg.innerHTML = one / two
break
}
}
</script>
</body>
</html>点击 "运行实例" 按钮查看在线实例
手写代码：
