不知道哪里错了，跪求大神们指点
<!DOCTYPE html>
<html>
<head>
<meta charset="UTF-8">
<title>VUE</title>
<script type="text/javascript"src="js/jquery-1.4.2.min.js"></script>
<script type="text/javascript">
function cli(){
var a = document.getElementById("a").value;
var b = document.getElementById("b").value;
var s = document.getElementById("s").value;
var c = document.getElementById("c").value;
if (s=="+") {
c=parseInt(a)+parseInt(b);
}else if (s=="-") {
c=parseInt(a)-parseInt(b);
}else if (s=="*") {
c=parseInt(a)*parseInt(b);
}else if (s=="/") {
c=parseInt(a)/parseInt(b);
};
}
</script>
</head>
<body>
<input type="text" value=""id="a">
<select name="" id="s">
<option value="+">+</option>
<option value="-">-</option>
<option value="*">*</option>
<option value="/">/</option>
</select>
<input type="text"value="" id="b">
<button onclick="cli()">=</button>
<input type="text" id="c">
</body>
</html>
