this.items = _.filter(this.items, item => _.find(this.dragSelection, x => x === item) === undefined); 这个代码是什么意思
时间: 2023-09-12 10:08:27 浏览: 51
这段代码是一个JavaScript箭头函数,主要作用是过滤掉this.items中与this.dragSelection中有相同元素的项。
具体来说,它使用了Underscore库中的filter函数,该函数接受一个集合和一个过滤器函数,返回所有满足条件的集合项。在这里,集合是this.items,过滤器函数是箭头函数item => _.find(this.dragSelection, x => x === item) === undefined。
箭头函数中的item表示集合中的每一项,而_.find(this.dragSelection, x => x === item)会在this.dragSelection中查找是否有元素与item相等,如果有,则返回该元素,否则返回undefined。如果_.find(this.dragSelection, x => x === item)返回undefined,说明this.dragSelection中不存在item元素,即item不在this.dragSelection中,则箭头函数的返回值为true,表示该项应该被保留。反之,如果_.find(this.dragSelection, x => x === item)返回了一个非undefined的元素,说明item与this.dragSelection中的某一项相等,即item应该被过滤掉。
因此,整个代码的含义是:过滤掉this.items中与this.dragSelection中有相同元素的项,并将过滤后的结果重新赋值给this.items。
相关问题
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.
用jquery 语法优化这段代码 obj.ele.find('.empty').hide(); obj.ele.find('.mini-listbox-item').each(function () { var $this = $(this); if ($this.text().indexOf(obj.value) > -1) { $this.removeClass('hidden'); } else { $this.addClass('hidden'); } }); if (obj.ele.find('.mini-listbox-item').length === obj.ele.find('.mini-listbox-item.hidden').length) { obj.ele.find('.empty').show(); }
可以使用链式调用、缓存 jQuery 对象和选择器、使用 ternary operator 等方式来优化代码,如下所示:
```
var $empty = obj.ele.find('.empty');
var $items = obj.ele.find('.mini-listbox-item');
var itemsLength = $items.length;
var hiddenItemsLength = $items.filter('.hidden').length;
$empty.toggle(hiddenItemsLength === itemsLength);
$items.each(function () {
var $this = $(this);
var isMatched = $this.text().indexOf(obj.value) > -1;
$this.toggleClass('hidden', !isMatched);
});
```
这样可以减少多次查询 DOM 元素,提高代码执行效率,并且可读性更好。
相关推荐
![rar](https://img-home.csdnimg.cn/images/20210720083606.png)
![zip](https://img-home.csdnimg.cn/images/20210720083736.png)
![rar](https://img-home.csdnimg.cn/images/20210720083606.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)
![](https://csdnimg.cn/download_wenku/file_type_ask_c1.png)