javascript-JavaScript做了個彈出層的form ，請問如何關閉form

JavaScript做了個彈出層的form ，請問如何關閉form

 <div class="form-control" id="sign_in" style="display:none">
        <input type="text" class="form-control" placeholder="Username">
        <input type="text" class="form-control" placeholder="password">
        <input type="button" class="btn btn-primary" value="sign in">
        <input type="button" class="btn btn-success" value="cancle">
 </div>
 <script>
            function signIn() {
                addBg();
                var alert_sign_in = document.getElementById("sign_in");
                alert_sign_in.style.display = "block";
                alert_sign_in.style.position = "absolute";
                alert_sign_in.style.top = "50%";
                alert_sign_in.style.left = "50%";
                alert_sign_in.style.marginTop = "-75px";
                alert_sign_in.style.marginLeft = "-150px";
                alert_sign_in.style.width = "500px";
                alert_sign_in.style.height = "700px";
                alert_sign_in.style.zIndex = "501";

              var mybg = document.createElement("div");
              mybg.setAttribute("id","mybg");
              mybg.style.background = "#000";
              mybg.style.width = "100%";
              mybg.style.height = "100%";
              mybg.style.position = "absolute";
              mybg.style.top = "0";
              mybg.style.left = "0";
              mybg.style.zIndex = "500";
              mybg.style.opacity = "0.3";
              mybg.style.filter = "alpha(opacity=30)";
              document.body.appendChild(mybg);

              document.body.style.overflow = "hidden";
            }
        </script>

這個是一個彈出式的登錄功能，先有個遮罩層，然後彈出一個form供用戶輸入信息，請問這個這個form如何關閉？就是用戶取消登錄的時候，遮罩層自動取消，然後form自動關閉。

彈出式的登錄功能是這樣寫的嗎？有沒有其他的寫法，謝謝。

最佳回答：

用JQUERY把form和遮罩層的div隱藏即可，或者移除

隱藏代碼
$("form的ID").hide();
$("div的ID").hide();

移除代碼
$("form的ID").remove();
$("div的ID").remove();