Vanilla javascript Trap 模式中的焦点（辅助功能选项卡）

这应该很简单，但由于某种原因它不起作用，我在正确的时间获得了正确的 console.logs，但焦点没有到达正确的位置，请参考我的 jsfiddle

https://jsfiddle.net/bqt0np9d/ https://jsfiddle.net/bqt0np9d/

function checkTabPress(e) {
    "use strict";
    // pick passed event of global event object
    e = e || event;

    if (e.keyCode === 9) {
        if (e.shiftKey) {
            console.log('back tab pressed');
            firstItem.onblur=function(){
                console.log('last a focus left');
                lastItem.focus();
            };
            e.preventDefault();
        }
        console.log('tab pressed');
        lastItem.onblur=function(){
            console.log('last a focus left');
            firstItem.focus();
        };
        e.preventDefault();
    }
}
modal.addEventListener('keyup', checkTabPress);

我必须将焦点锁定在我们在 React 组件中使用的模式中。 我为 KEYDOWN 添加了事件监听器并收集了 Tab 和 Shift+Tab

class Modal extends Component {
    componentDidMount() {
        window.addEventListener("keyup", this.handleKeyUp, false);
        window.addEventListener("keydown", this.handleKeyDown, false);
    }

    componentWillUnmount() {
        window.removeEventListener("keyup", this.handleKeyUp, false);
        window.removeEventListener("keydown", this.handleKeyDown, false);
    }

    handleKeyDown = (e) => {

        //Fetch node list from which required elements could be grabbed as needed.
        const modal = document.getElementById("modal_parent");
        const tags = [...modal.querySelectorAll('select, input, textarea, button, a, li')].filter(e1 => window.getComputedStyle(e1).getPropertyValue('display') === 'block');
        const focusable = modal.querySelectorAll('button, [href], input, select, textarea, li, a,[tabindex]:not([tabindex="-1"])');
        const firstFocusable = focusable[0];
        const lastFocusable = focusable[focusable.length - 1];

        if (e.ctrlKey || e.altKey) {
            return;
        }

        const keys = {
            9: () => { //9 = TAB
                if (e.shiftKey && e.target === firstFocusable) {
                    lastFocusable.focus();
                }

                if (e.target === lastFocusable) {
                    firstFocusable.focus();
                }
            }
        };

        if (keys[e.keyCode]) {
            keys[e.keyCode]();
        }
    }
}