function $(param) { var domList = []; if (param.indexOf('#') == 0) { var id = param.substring(1); var dom = document.getElementById(id); domList[0] = dom; } else if (param.indexOf('.') == 0) { var name = param.substring(1); domList = document.getElementsByName(name); } else { domList = document.getElementsByTagName(param); } domList.prop = function () { if (arguments.length == 1) { var dom = domList[0]; return dom[arguments[0]]; } else if (arguments.length == 2) { for (let i = 0; i < domList.length; i++) { var dom = domList[i]; dom[arguments[0]] = arguments[1]; } } } return domList; }帮我解释一下这些代码

这段代码定义了一个名为 `$` 的函数，该函数可以根据参数返回一个或多个DOM节点（元素）。

函数接受一个参数，参数可以是标签名、类名或ID。如果参数以 `#` 开头，则返回ID匹配的DOM节点；如果参数以 `.` 开头，则返回类名匹配的DOM节点；否则，返回标签名匹配的DOM节点。

代码中定义了一个 `domList` 数组来存储匹配的DOM节点。如果参数为ID，则使用 `document.getElementById()` 方法获取DOM节点，并将其存储在 `domList` 数组的第一个元素中。如果参数为类名，则使用 `document.getElementsByName()` 方法获取DOM节点，并将其存储在 `domList` 数组中。如果参数为标签名，则使用 `document.getElementsByTagName()` 方法获取DOM节点，并将其存储在 `domList` 数组中。

此外，函数还定义了一个 `prop()` 方法来设置或获取DOM节点的属性。当 `prop()` 方法接收一个参数时，它将返回第一个DOM节点的指定属性的值。当 `prop()` 方法接收两个参数时，它将设置所有DOM节点的指定属性为指定的值。

最后，该函数返回 `domList` 数组，该数组包含匹配的DOM节点。可以链式调用该函数来对匹配的DOM节点进行操作。

相关问题

layui.define(["jquery"], function (exports) { var $ = layui.$; var miniTongji = { /** * 初始化 * @param options */ render: function (options) { options.specific = options.specific || false; options.domains = options.domains || []; var domain = window.location.hostname; if (options.specific === false || (options.specific === true && options.domains.indexOf(domain) >=0)) { miniTongji.listen(); } }, /** * 监听统计代码 */ listen: function () { var _hmt = _hmt || []; (function () { var hm = document.createElement("script"); hm.src = "https://hm.baidu.com/hm.js?d97abf6d61c21d773f97835defbdef4e"; var s = document.getElementsByTagName("script")[0]; s.parentNode.insertBefore(hm, s); })(); } }; exports("miniTongji", miniTongji); });

这段代码是一个使用了layui框架的JavaScript模块，其中定义了一个名为miniTongji的模块，该模块主要用于初始化和监听百度统计代码。在初始化时，可以传入一个options对象，其属性包括specific和domains，分别表示是否仅在特定域名下生效和特定域名列表。在listen函数中，通过创建一个script标签并设置src属性，来加载百度统计的JavaScript代码。最后，通过layui的exports函数将miniTongji模块导出。

优化此代码 const openKeys = ref<string[]>([]) const selectedKeys = ref<string[]>([]) const { currentMenu, currentMenuTree, currentMenuList } = storeToRefs( useLayoutStore(), ) const rootSubmenuKeys = currentMenuList.value.filter((v: any) => { if (v.type === 0) { return v.parentId } }) watch( () => currentMenu, () => { openKeys.value = [currentMenu.value?.parentId] selectedKeys.value = [currentMenu.value?.id] }, { immediate: true }, ) const router = useRouter() /** * 点击事件 * @param e 事件对象 */ const handleClick = (e: any) => { const item = currentMenuList.value.find((_) => _.id === e.key) if (item) { router.push(item.path) } } /** * SubMenu 展开/关闭的回调 * @param e 展开的openKeys */ const onOpenChange = (e: any) => { const latestOpenKey = e.find((key: any) => openKeys.value.indexOf(key) === -1) if (rootSubmenuKeys.indexOf(latestOpenKey) === -1) { openKeys.value = e } else { openKeys.value = latestOpenKey ? [latestOpenKey] : [] } }

There are a few optimizations that could be made to this code:

1. Instead of using `ref` for `openKeys` and `selectedKeys`, you can use `reactive` to make the code more concise:

   const state = reactive({
     openKeys: [],
     selectedKeys: [],
   })

2. Instead of using `storeToRefs` to convert the store state to refs, you can use the `toRefs` function, which is shorter and more concise:

   const { currentMenu, currentMenuTree, currentMenuList } = toRefs(useLayoutStore())

3. Instead of using `watch` to watch the `currentMenu` state changes, you can use a computed property to update the `openKeys` and `selectedKeys` arrays:

   const selectedMenu = computed(() => {
     const item = currentMenuList.value.find((_) => _.id === currentMenu.value?.id)
     return [item?.id] || []
   })

   const parentMenu = computed(() => {
     const item = currentMenuList.value.find((_) => _.id === currentMenu.value?.parentId)
     return [item?.id] || []
   })

   watch([selectedMenu, parentMenu], ([selected, parent]) => {
     state.selectedKeys = selected
     state.openKeys = parent
   })

4. Instead of using `router.push` in the `handleClick` function, you can use the `router.push` method directly in the template:

   <Menu.Item :key="item.id" :to="item.path">{{ item.name }}</Menu.Item>

5. Finally, instead of using `rootSubmenuKeys` to filter the list of menu items, you can use a computed property to filter the list of menu items based on their type:

   const subMenuItems = computed(() => {
     return currentMenuList.value.filter((v: any) => v.type === 0 && v.parentId)
   })

By applying these optimizations, the code can be simplified and made more concise.