Vue and Element-UI cascade drop-down box lazy loading

The Element-UI cascading drop-down box does not support lazy loading and needs to be implemented manually. The core of lazy loading is to only load data at the current visible level, and then load child node data asynchronously when nodes are expanded. The key to implementation lies in the load method, which triggers asynchronous loading when the node is clicked through the @node-click event. Pay attention to performance optimization points such as data format optimization, caching mechanism, error handling and unlimited loading strategies.

Vue and Element-UI cascaded drop-down box lazy loading: performance optimization tool

Many friends will encounter the problem of huge data volume of cascading selection boxes causing page stuttering when developing with Vue and Element-UI. This article will talk about how to solve this problem gracefully - lazy loading. After reading it, you will understand the principle of lazy loading, learn how to implement it efficiently, and avoid some common pitfalls.

Let's clarify first: The cascading selection box of Element-UI does not directly support lazy loading. This means we need to do it ourselves and have enough food and clothing. This cannot be done in just a few lines of code. It requires a deeper understanding of Vue's responsive mechanism and asynchronous operations.

Let's start with the basics. The cascading selection box is essentially a tree-shaped data display and selection component. If the data volume is large, directly loading all data will cause excessive rendering burden on the browser, resulting in slow loading of the page or even crashing. The core idea of ​​lazy loading is: only load data at the current visible level, and the user needs to expand the next level before loading the corresponding data.

The key to implementing lazy loading lies in the load method. The cascading selection box of Element-UI provides a @node-click event, which is triggered when the node is clicked. We can use this event to load child node data asynchronously when nodes are expanded.

Let’s take a look at an example, suppose our data structure is like this:

 <code class="javascript">const data = [ { value: '1', label: '一级菜单1', children: [] // 懒加载，初始为空}, { value: '2', label: '一级菜单2', children: [] // 懒加载，初始为空} ];</code>

Then, in our Vue component:

 <code class="vue"><template> <el-cascader v-model="value" :options="data" :props="props"></el-cascader> </template> <script> import { ref, reactive } from &#39;vue&#39;; export default { setup() { const value = ref([]); const data = reactive([ { value: &#39;1&#39;, label: &#39;一级菜单1&#39;, children: [] }, { value: &#39;2&#39;, label: &#39;一级菜单2&#39;, children: [] } ]); const props = reactive({ label: &#39;label&#39;, value: &#39;value&#39;, children: &#39;children&#39; }); const handleNodeClick = async (node, data) => { if (!node.children && node.children !== undefined) { //只加载未加载的节点node.loading = true; // 显示加载状态const res = await fetch(`/api/data?parentId=${node.value}`); // 异步获取子节点数据const children = await res.json(); node.children = children; node.loading = false; // 隐藏加载状态} }; return { value, data, props, handleNodeClick }; } }; </script></code>

In this code, the handleNodeClick method will be triggered when the node is clicked. If the node does not have child nodes ( !node.children ), it requests data from the backend and assigns the data to node.children . node.loading is used to display the loading status and improve the user experience. Remember, fetch is an asynchronous operation, be sure to use await to wait for the result.

It should be noted that the backend interface /api/data?parentId=${node.value} needs to return the corresponding child node data according to the parent node's value . This part needs to be adjusted according to your actual backend interface.

Regarding performance optimization, there are several other points that need special attention:

• Data format optimization: The data format returned by the backend should be as concise as possible to avoid unnecessary fields.
• Caching mechanism: You can consider using the caching mechanism to reduce the number of requests to the backend. For example, you can use localStorage or sessionStorage to cache the loaded data.
• Error handling: To deal with network request failures to avoid program crashes. For example, you can add try...catch statement to catch exceptions.
• Unlimited loading: If your data hierarchy is deep, you may need to consider unlimited loading strategies to avoid loading too much data.

In short, the lazy loading implementation of Vue and Element-UI cascaded drop-down boxes requires careful consideration of data structure, asynchronous operations, error handling, and caching mechanisms. This article provides a basic implementation solution that I hope can help you solve practical problems. Remember, practice to achieve true knowledge and try more hands-only to truly master this technology. Don't forget to adjust the code according to your actual situation and conduct sufficient testing.

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