使用html+javascriptt实现的简易四则运算（初学JavaScript笔记）

今天第一天学javascript，做了个简易的四则运算，提供参考，效果图：

使用html+javascriptt实现的简易四则运算（初学JavaScript笔记）-LMLPHP

html代码：

<!DOCTYPE html>

<html >

<head >

<meta charset="UTF-8">

<link rel="stylesheet" type = "text/css"  href = "css/1.css">

<title>index</title>

</head>

<body id="a1">

<script type="text/javascript" src = "js/3.js">

</script>

<form>

<p >

 <input id = "1" type="text" size="20px" name="a "  onkeyup="this.value=this.value.replace(/[^\d]/ig,'')"/>

 <select id = "c">

        <option id = "jia" value="+">+</option>

        <option id = "jian" value="-">-</option>

        <option id = "cheng" value="*">*</option>

        <option id = "chu" value="/">/</option>

 </select>

 <input id = "2" type="text" size="20px" name="b"  onkeyup="this.value=this.value.replace(/[^\d]/ig,'')"/>

 =

 <input id = "3" type="text" size="20px" name="result "  onkeyup="this.value=this.value.replace(/[^\d]/ig,'')"/>

 <input name = "button" type = "button" value= "点击提交" onclick = "cal()">

 </p>

</form>

</body>

</html>

js代码：

function  cal(){

        var numa,numb,cc,sum;

        numa = Number(document.getElementById("1").value);

        numb = Number(document.getElementById("2").value);

        cc = document.getElementById("c").value;

        if(cc == "+"){

            sum = numa + numb;

        }else if(cc=="-"){

            sum = numa - numb;

        }else if(cc=="*"){

            sum = numa * numb;

        }else{

            sum = numa / numb;

        }

        document.getElementById("3").value= sum;

        //alert("计算结果："+sum);

        //document.write(sum);

    }