将焦点移到"下一步""li"忽略所有嵌套元素的元素

Question

我的菜单的结构如下。

$('html').removeClass('no-js');
// Add plus mark to li that have a sub menu
$('li:has("ul") > a').append('<span class="plusMark">+</span>');
Mousetrap.bind('down', function(e) {
  if ($(".manu-t").children("ul").children("li").children(":focus").length != 0) {
    //mentioned below What I have tried till now
  }
});

#nav,
#nav ul,
#nav li {
  margin: 0;
  padding: 0;
  border: 0;
  list-style: none;
  box-sizing: border-box;
}
#nav {
  position: relative;
  min-height: 30px;
  max-width: 100%;
  background-color: #b5b5b5;
  color: #000;
}
#nav li {
  position: relative;
}
#nav a {
  text-decoration: none;
  height: 100%;
  display: block;
  padding: 0 20px;
}
#nav>ul,
.fa {
  height: 30px;
  line-height: 30px;
}
#nav>ul>li {
  position: relative;
  text-align: center;
}
#nav>ul>li>a {
  background-color: #b5b5b5;
}
#nav>ul>li>a:hover,
#nav>ul>li>a:focus,
#nav>ul>li>a.js-openSubMenu {
  background-color: #5f5f5f;
}
#nav>ul>li:hover>a,
#nav>ul>li:focus>a {
  background-color: #5f5f5f;
  color: #fff;
}
#nav>ul>li>ul>li>a {
  background-color: #5f5f5f;
}
#nav>ul>li>ul>li>a:hover,
#nav>ul>li>ul>li>a:focus {
  background-color: #b5b5b5;
}
#nav>ul>li>ul>li:not(:last-child) a {
  border-bottom: 1px solid #b5b5b5;
}
#nav>ul>li>ul>li>ul>li>a {
  background-color: #b5b5b5;
}
#nav>ul>li>ul>li>ul>li>a:hover,
#nav>ul>li>ul>li>ul>li>a:focus {
  background-color: #5f5f5f;
}
#nav>ul>li>ul>li>ul>li:not(:last-child)>a {
  border-bottom: 1px solid #5f5f5f;
}
/* Javascript classes */
#nav .js-hideElement {
  display: none;
}
#nav .js-showElement {
  display: block;
}

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="containe-header">
  <nav id="nav">
    <ul>
      <li class="menu-t"><a href="#">Main</a>
        <ul>
          <li><a href="#">Item1</a>
            <ul>
              <li><a href="#">Sub Item 1</a></li>
              <li><a href="#">Sub Item 2</a></li>
              <li><a href="#">Sub Item 3</a></li>
              <li><a href="#">Sub Item 4</a></li>
            </ul>
          </li>
          <li><a href="#">Item2</a>
            <ul>
              <li><a href="#">Sub Item 1</a></li>
              <li><a href="#">Sub Item 2</a></li>
              <li><a href="#">Sub Item 3</a></li>
              <li><a href="#">Sub Item 4</a></li>
              <li><a href="#">Sub Item 5</a></li>
              <li><a href="#">Sub Item 6</a></li>
            </ul>
          </li>
          <li><a href="#">Item3</a></li>
          <li><a href="#">Item4</a></li>
        </ul>
      </li>
      <li class="menu-l"><a href="#">Menu2</a></li>
    </ul>
  </nav>
</div>

问题是将焦点从item1转到item2和item3上，又要在...下按下箭头键（我已经使用Mousetrap库来检测按键）

我到目前为止尝试过的。

1。

var focused_index = 1;
focused_index=focused_index - 1;
$('a').eq(focused_index).focus();

但是，此方法着重于嵌套元素的意思是从项目1到子项目1，然后再到子项目2等。

2。

// Get the focused element:
var $focused = $(':focus');
// No jQuery:
var focused = document.activeElement;
// Does the element have focus:
var hasFocus = $('foo').is(':focus');
// No jQuery:
elem === elem.ownerDocument.activeElement;

，但这会导致其他元素在身体内部的焦点。

3. 这个问题的回答将焦点发送到Dynamic Li with Jquery

所以我如何将焦点从item1转移到项目2。

Answer 1

我想关注item2的元素。然后转到项目3的元素。

您可以使用：

$("a:focus").closest("li").next().find("a").first().focus();

工作片段：

// Add plus mark to li that have a sub menu
$('li:has("ul") > a').append('<span class="plusMark">+</span>');
// set initial focus
$("#nav>ul>li.menu-t>ul>li>a:first()").focus();
$(document).on("keydown", function(e) {
  if (e.keyCode == 40) {
     $("a:focus").closest("li").next().find("a").first().focus();
     return false;
  } 
  if (e.keyCode == 38) {
     $("a:focus").closest("li").prev().find("a").first().focus();
     return false;
  }
  
  //if ($(".manu-t").children("ul").children("li").children(":focus").length != 0) {
    //mentioned below What I have tried till now
  //}
});

a { text-decoration: none; }
:focus { background-color: yellow; }

<script src="https://cdnjs.cloudflare.com/ajax/libs/jquery/3.3.1/jquery.min.js"></script>
<div class="containe-header">
  <nav id="nav">
    <ul>
      <li class="menu-t"><a href="#">Main</a>
        <ul>
          <li><a href="#">Item1</a>
            <ul>
              <li><a href="#">Sub Item 1</a></li>
              <li><a href="#">Sub Item 2</a></li>
              <li><a href="#">Sub Item 3</a></li>
              <li><a href="#">Sub Item 4</a></li>
            </ul>
          </li>
          <li><a href="#">Item2</a>
            <ul>
              <li><a href="#">Sub Item 1</a></li>
              <li><a href="#">Sub Item 2</a></li>
              <li><a href="#">Sub Item 3</a></li>
              <li><a href="#">Sub Item 4</a></li>
              <li><a href="#">Sub Item 5</a></li>
              <li><a href="#">Sub Item 6</a></li>
            </ul>
          </li>
          <li><a href="#">Item3</a></li>
          <li><a href="#">Item4</a></li>
        </ul>
      </li>
      <li class="menu-l"><a href="#">Menu2</a></li>
    </ul>
  </nav>
</div>

Answer 2

您可以使用CSS选择器将要"焦点"的元素存储在数组中。为"键盘"事件添加事件处理程序 - 如果e.code显示用户单击向下箭头，然后迭代到数组中的下一个元素。我通过使用一个发电机函数来完成此操作，该函数在到达数组的末端时会旋转到0索引：

function* nextElGenerator() {
  var liEls = document.querySelectorAll('.menu-t > ul > li > a:first-child');
  var i = 0;
  while (true) {
    yield liEls[i];
    i += 1;
    if (i === liEls.length) {
      i = 0;
    }
  }
}
const bulletElItr = nextElGenerator();
let curEl;
document.addEventListener('keydown', e => {
  if (e.code === 'ArrowDown') {
    if (curEl) {
      curEl.style.backgroundColor = 'transparent';
    }
    curEl = bulletElItr.next().value;
    curEl.style.backgroundColor = 'yellow';
  }
});

<div class="containe-header">
  <nav id="nav">
    <ul>
      <li class="menu-t"><a href="#">Main</a>
        <ul>
          <li><a href="#">Item1</a>
            <ul>
              <li><a href="#">Sub Item 1</a></li>
              <li><a href="#">Sub Item 2</a></li>
              <li><a href="#">Sub Item 3</a></li>
              <li><a href="#">Sub Item 4</a></li>
            </ul>
          </li>
          <li><a href="#">Item2</a>
            <ul>
              <li><a href="#">Sub Item 1</a></li>
              <li><a href="#">Sub Item 2</a></li>
              <li><a href="#">Sub Item 3</a></li>
              <li><a href="#">Sub Item 4</a></li>
              <li><a href="#">Sub Item 5</a></li>
              <li><a href="#">Sub Item 6</a></li>
            </ul>
          </li>
          <li><a href="#">Item3</a></li>
          <li><a href="#">Item4</a></li>
        </ul>
      </li>
      <li class="menu-l"><a href="#">Menu2</a></li>
    </ul>
  </nav>
</div>