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实例
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>迷你计算器</title>
<style type="text/css">
.box{
width:500px;
height:200px;
background-color:#efefef;
border:1px solid lightgray;
text-align:center;
margin:20px auto;
color:#636363;
border-radius:15px;
box-shadow:8px 8px 8px #999;
}
table{
margin:auto;
border:1px solid blue;/*这框看得清楚*/
}
td{
width:100px;
height:30px;
padding:5px 0px;
border:1px solid red;/*这红框看得老清楚了,代码写到这儿计算按钮出去了，调了个参数*/
}
input.select{
width:100%;
height:100%;
border:none;
text-align:center;
background-color:cyan;
}
button{
width:100%;
height:100%;
border:none;
background-color:skyblue;
color:white;
}
button:hover{
cursor:pointer;
background-color: coral;
width:105%;
height:105%;
}
</style>
</head>
<body>
<div class="box">
<h2>迷你计算器</h2>
<form>
<table>
<tr>
<td><input type="text" name="opt1" placeholder="操作数1"></td>
<td>
<select name="option">
<option value="null">请选择操作</option>
<option value="add">+</option>
<option value="sub">-</option>
<option value="mul">*</option>
<option value="div">/</option>
</select>
</td>
<td><input type="text" name="opt2" placeholder="操作数2"></td>
<td><button type="button">计算</button></td>
</tr>
<tr>
<td colspan="2" align="right"><h3>结果：</h3></td>
<td colspan="2" align="left"><h3 id="placeholder"></h3></td>
</tr>
</table>
</form>
</div>
<script>
//1.获取操作数，按钮与结果占位符
var opt1=document.getElementsByName('opt1')[0]
var opt2=document.getElementsByName('opt2')[0]
var opt=document.getElementsByName('option')[0]
var btn=document.getElementsByTagName('button')[0]
var placeholder=document.getElementById('placeholder')
//2.已获取界面提交参数，执行计算操作
btn.onclick=function(){
var data1=parseFloat(opt1.value)
var data2=parseFloat(opt2.value)
if(opt1.value.length==0){
alert('第一个操作数不能为空')
opt1.focus()
return false
}else if (isNaN(opt1.value)) {
alert('第一个操作数必须为数字')
opt1.focus()
return false
}else if(opt2.value.length==0){
alert('第二个操作数不能为空')
opt2.focus()
return false
}else if(isNaN(opt2.value)){
alert('第二个操作数必须为数字')
opt2.focus()
return false
}else{
var data1=parseFloat(opt1.value)
var data2=parseFloat(opt2.value)
}
var option=opt.value
var temp=0
var flag=''
var result = ''
switch (option){
case 'null':
alert("请选择操作类型")
opt.focus()
return false
case 'add':
flag = '+'
temp = data1 + data2
break
case 'sub':
flag = '-'
temp = data1 - data2
break
case 'mul':
flag = '*'
temp = data1 * data2
break
case 'div':
flag = '/'
if (data2 == 0) {
alert('除数不能为0,请重新输入')
opt2.focus()
return false
} else {
temp = data1 / data2
}
break
}
var str = '<span style="color:coral">'
str += data1+' '+flag+' '+data2 + ' = ' + temp
str += '</span>'
placeholder.innerHTML = str
}
</script>
</body>
</html>
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