The key to optimizing the Vue and Element-UI cascading drop-down boxes is data processing and rendering strategies. The specific methods include: lazy loading: load data on demand, loading only data visible to users. Virtual scrolling: Only render data in the visible area of ??the screen, and improve scrolling performance through dynamic updates.

Vue and Element-UI cascading drop-down box performance optimization: Don't let your users wait too long!

Many students have encountered this problem: a seemingly simple cascading drop-down box on the page, and when the data volume is large, it will become like a snail. The user experience collapses directly, and this is not a joke. In this article, let’s talk about how to optimize the cascading drop-down box of Vue and Element-UI to make it fly!

Let’s talk about the conclusion first: the key to optimization lies in data processing and rendering strategies. Don’t think about getting it in one step. Optimization is an iterative process. First solve the most obvious problems, and then gradually refine them.

Basic knowledge review: You need to understand some Vue and Element-UI

This article assumes that you already have some understanding of Vue and Element-UI and know how to use el-cascader . don't know? Go and learn quickly! Don't expect me to teach you the basic grammar of Vue step by step.

Element-UI's el-cascader component is easy to use, but it does not make special optimizations for super large data volumes. Its default rendering method, once the data volume is large, it will directly lie down the browser. It's like using a sedan to pull a brick. It can be pulled, but it's extremely inefficient and can easily break the car.

Core concepts: lazy loading and virtual scrolling, your secret weapon

Optimizing the cascading drop-down box, the core is two words: lazy loading and virtual scrolling.

Lazy loading, to put it bluntly, loading data on demand. Don’t just stuff all the data into the component at the beginning. Users only see the first level. Why do you load the second and third level data? Wait until the user expands to the second level, then loads the data at the second level; and so on. It's like ordering dishes. You only ordered one dish. Why did the restaurant make all the dishes?

Virtual scrolling, more advanced. It only renders data in the visible area of ??the screen, and data in the invisible area is not rendered, and is only saved in memory. When the user scrolls, the data in the visible area is updated dynamically. It's like a super long list, you only see the parts on the screen, not the entire list is rendered.

Code example: Optimize cascading drop-down boxes with lazy loading

Let's assume your data structure is like this:

 <code class="javascript">const data = [ { value: '1', label: '一級菜單1', children: [ { value: '1-1', label: '二級菜單1-1', children: [{value: '1-1-1', label: '三級菜單1-1-1'}] }, { value: '1-2', label: '二級菜單1-2', children: [{value: '1-2-1', label: '三級菜單1-2-1'}] } ] }, { value: '2', label: '一級菜單2', children: [ /* ... */ ] } // ... 更多一級菜單];</code>

Using lazy loading, you can rewrite it like this:

 <code class="vue"><template> <el-cascader v-model="selectedOptions" :options="options" :props="{ checkStrictly: true, value: 'value', label: 'label', children: 'children' }"></el-cascader> </template> <script> export default { data() { return { selectedOptions: [], options: [], // 初始化為空數(shù)組loadedData: {} // 緩存已加載的數(shù)據(jù)}; }, methods: { loadOptions(parentId = null) { // 模擬從服務(wù)器加載數(shù)據(jù)，parentId 為父級菜單的value return new Promise(resolve => { setTimeout(() => { const levelData = this.filterData(data, parentId); this.loadedData[parentId || &#39;&#39;] = levelData; resolve(levelData); }, 500); // 模擬網(wǎng)絡(luò)延遲}); }, filterData(data, parentId) { // 過濾出對應(yīng)父級的數(shù)據(jù)if (parentId === null) return data; return data.find(item => item.value === parentId)?.children || []; }, async handleChange(value) { // 根據(jù)選擇的節(jié)點加載下一級數(shù)據(jù)const lastSelected = value[value.length - 1]; if (!this.loadedData[lastSelected]) { const nextLevelOptions = await this.loadOptions(lastSelected); this.options = this.options.concat(nextLevelOptions); } }, // ... 其他方法} }; </script></code>

Virtual scrolling: More advanced optimizations, but more complex

Virtual scrolling requires the help of some libraries, such as vue-virtual-scroller . Its principle is quite complicated, so I won’t go into details here. Interested students can study it on their own. The core idea is to render only visible areas and optimize scroll events.

Performance Optimization and Best Practice: Details Determine Success or Failure

• Data preprocessing: Process data on the backend to reduce the burden of front-end processing. For example, the data can be layered and only the necessary data can be returned.
• Data format optimization: Choose the right data structure to avoid unnecessary nesting.
• Caching: Use browser cache or local cache to reduce duplicate requests.
• Code specification: Write efficient and maintainable code.

Remember, optimization is a gradual process, don't expect to be done in one step. First solve the most obvious problem, and then gradually optimize the details. Only by using browser developer tools can you analyze performance bottlenecks in a targeted manner. Don't forget, user experience is paramount!

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