简单javascript问题在线等

晕，你滴大括号不匹配！！！删除第 20 滴大括号！！！<script type="text/javascript" language="javascript">
    function userCheck(){
    var f=document.form1;
    var username=f.username.value;
    if(username=""){
    window.alert("用户名不能为空！")
    f.username.focus();
    return false;
    }
    else
    {
    //send_request('check.jsp?username'=+username);
    }
    }
    //} 删除它~~~，哈
</script>