计算器
代码：
<!DOCTYPE html>
<html lang="en">
<head>
<meta charset="UTF-8">
<title>Document</title>
<script type="text/javascript">
window.onload = function(){
var con1 = document.getElementById('header')
var con2 = document.getElementById('footer')
var con3 = document.getElementById('select')
var con4 = document.getElementById('btn')
var sum;
con4.onclick = function(a,b,c){
if(isNaN(con1.value) || isNaN(con2.value)){
alert("输入格式不对,请重新输入")
}
else{
if(con3.value == 0){
sum = +con1.value + con2.value*1;
alert(parseInt(sum*100)/100);
}
else if(con3.value == 1){
sum = +con1.value - con2.value*1;
alert(parseInt(sum*100)/100);
}
else if(con3.value == 2){
sum = +con1.value * con2.value*1;
alert(parseInt(sum*100)/100);
}
else if(con3.value == 3){
if(con2.value != 0){
sum = (+con1.value*100) / (con2.value*100);
alert(parseInt(sum*100)/100);
}
else{
alert("0不能作除数")
}
}
}
}
}
</script>
</head>
<body>
<input type="text" name="" id="header">
<select name="" id="select">
<option value="0">+</option>
<option value="1">-</option>
<option value="2">*</option>
<option value="3">/</option>
</select>
<input type="text" name="" id="footer">
<input type="button" name="" value="计算" id="btn">
</body>
</html>
效果：
image.png
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