请问我这儿哪里出错了,无法运行出来
<!DOCTYPE HTML>
<html >
<head>
<meta http-equiv="Content-Type" content="text/html; charset=utf-8" />
<title>函数</title>
<script type="text/javascript">
function asd()
{
var x,y;
x=parseInt(prompt("输入第一个数:"));
y=parseInt(prompt("输入第二个数:"));
if(x>y){
document.write(x+"大");
}
else if(x=y){
document.write("相等");
}
else{
document.write(y+"大");
}
</script>
</head>
<body>
<input type="botton" value="点我" onclick="asd()">
</body>
</html>