Jquery Selector无法在Polymer中找到div元素。应该是直截了当不理解问题

Question

目标：单击表单内的图标我想向包含表单的div添加一个新类。问题：pullupClose中的Jquery选择器没有拾取元素。 Console.log result of Jquery sector in this image.由于元素只是没有获取，因此addAclass不起作用。你能搞清楚我在做错吗？提前致谢

html

<div class="sidepullup" id="idSidePullup">
            <iron-icon class="cross" on-click="pullupClose" icon="close"></iron-icon>
            <iron-form id="idForm">
                <form action="/">
                    <paper-input type"text" label="First Name"></paper-input>
                    <paper-input type="text" label="Last Name"></paper-input>
                    <paper-input type="text" label="Title"></paper-input>
                    <paper-input type="text" label="About"></paper-input>
                    <paper-button style="background-color: #03a9f4; color: white" raised onclick="onFormSubmit()">Submit Changes</paper-button>
                </form>
            </iron-form>
         </div>

脚本

<script>
        class IronListClass extends Polymer.Element {
            static get is() {return 'iron-comp'}
        ready() {
                super.ready();
                var that = this;
            }
            pullupClose() {
                var element = $("#idSidePullup");
                console.log('console log of $("#idSidePullup") = ', element);
                $("#idSidePullup").addClass('hidePullup');
                $("#idSidePullup").css("display", "none");
            }
window.customElements.define(IronListClass.is, IronListClass);
    </script>