JavaScript简单计算器 -

<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>简单计算器</title>
</head>
<body>
<div>
    <input type="text" id="num1" value="">
    <select id="yunsuanfu">
        <option value="请选择">请选择</option>
        <option value="+">+</option>
        <option value="-">-</option>
        <option value="*">*</option>
        <option value="/">/</option>
        <option value="%">%</option>
    </select>
    <input type="text" id="num2" value="">
    <button id="count">
        计算
    </button>
    <p id="jieguo"></p>
</div>
</body>
<script>
    var count = document.getElementById('count');
    count.onclick = function(){
        var num1 =document.getElementById('num1').value;
        var num2 =document.getElementById('num2').value;
        var yunsuanfu =document.getElementById('yunsuanfu').value
        var re = /^[0-9]+.?[0-9]*/;
        if (num1 =='' || num2 ==''){
            document.getElementById('jieguo').innerHTML= '错误：计算不能为空'
        }
        else if(num2 == 0 && (yunsuanfu =='/' || yunsuanfu == '%')){
            document.getElementById('jieguo').innerHTML= '错误：被除数不能为0'
        }
        else if(!re.test(num1) || !re.test(num2)){
            document.getElementById('jieguo').innerHTML= '错误：只能填写数字进行计算'
        }
        else {
            num1 = parseFloat(num1);
            num2 = parseFloat(num2);
            console.log(num1)
            console.log(num2)
            if(yunsuanfu == '请选择'){
                document.getElementById('jieguo').innerHTML='请选择运算符';
            }
            if(yunsuanfu == '+'){
                document.getElementById('jieguo').innerHTML=num1+'+'+num2+'='+(num1+num2);
            }
            if(yunsuanfu == '-'){
                document.getElementById('jieguo').innerHTML=num1+'-'+num2+'='+(num1-num2);
            }
            if(yunsuanfu == '*'){
                document.getElementById('jieguo').innerHTML=num1+'*'+num2+'='+(num1*num2);
            }
            if(yunsuanfu == '/'){
                document.getElementById('jieguo').innerHTML=num1+'除'+num2+'='+(num1/num2);
            }
            if(yunsuanfu == '%'){
                document.getElementById('jieguo').innerHTML=num1+'取余'+num2+'='+(num1%num2);
            }
        }
    }
</script>
</html>