版权声明：本文为博主原创文章，未经博主允许不得转载。 https://blog.csdn.net/Yonggie/article/details/89669848
带有enter键出结果，
可以直接复制粘贴。
<html>
<head>
</head>
<title> calculator</title>
<script src="jquery-3.3.1.min.js"> </script>
<style>
#container{
margin:0 auto;
text-align:center;
}
input{
width:100px;
}
</style>
<body>
<center><h1>xxx计算器，用了都说好！</h1></center>
<div id="container">
<input type=text id="first"/>
<select id="op">
<option>+</option>
<option>-</option>
<option>*</option>
<option>/</option>
</select>
<input type=text id="second"/>
<span> = </span>
<span id="result"> </span>
<br><br><br>
<button id="do" onclick="cal()">计算</button>
</div>
<script>
//1.2+2.4===3.5999999996
function cal(){
var first = parseFloat($("#first").val());
console.log(first);
var second=parseFloat($("#second").val());
console.log(second);
var op=$("#op").val();
if(isNaN(first)||isNaN(second)) alert("input is not a number! please re-input!");
else {
if(op==='+') $('#result').html(first+second);
else if(op==='-')$('#result').html(first-second);
else if(op==='/')$('#result').html(first/second);
else if(op==='*')$('#result').html(first*second);
}
}
$(function(){
document.onkeydown=(function(event){
var ev=document.all?window.event:event;
if(ev.keyCode==13) cal();
});
});
</script>
</body>
</html>