onsubmit="return false" 无效果应该怎么改进

<form action="/form1" method="post" onsubmit="return check()">
    <h1>
        留言
    </h1>
    企业名称
    <input type="text"name="enterprise" id="enterprise">
    <br>
    移动电话
    <input type="text" name="phone" id="phone">
    <br>
    <input type="submit">
</form>
<script>
    function check() {
        var aa=Document.getElementById("enterprise").value;
        if(aa==""){
            alert("信息为空！")
            return false;
        } else{
            return true;
        }
    }

@WebServlet(name="Form1Servlet",urlPatterns = "/form1")
public class Form1Servlet extends javax.servlet.http.HttpServlet {
    protected void doPost(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {
        String enterprise=request.getParameter("enterprise");
        String phone=request.getParameter("phone");
        response.sendRedirect("/form1Result.html");
    }

    protected void doGet(javax.servlet.http.HttpServletRequest request, javax.servlet.http.HttpServletResponse response) throws javax.servlet.ServletException, IOException {

    }
}

运行之后不管输入与否都会跳转到form1Result.html， onsubmit="return check()"这句话好像没有效果

但我想想让enterprise不为空时才跳转该、enterprise为空时不跳转，应该怎么改动

获取input的语法错了

var aa=document.getElementById("enterprise").value;