Vue and Element-UI cascaded drop-down boxes to implement paging function requires: asynchronous loading of data: gradually loading the next level of data according to user selection. Paging parameters: When requesting the server, pass paging parameters (page number, page size), and the server returns the paged data and total data volume. Pagination component: Use the el-pagination component of Element-UI to display the paging and update the paging properties based on the total data volume. Common errors: Handle asynchronous request errors to ensure that paging parameters are correctly passed and processed. Performance optimization: Consider virtual scrolling, data caching and reasonable data structure design.

Vue and Element-UI cascaded drop-down box pagination: a game of performance and experience

Many students will encounter huge data volumes of cascading drop-down boxes when using Vue and Element-UI to do projects. Imagine that there are dozens of cities under a province, and hundreds of districts and counties under each city... If all the data is directly stuffed into the cascading drop-down box, the browser will be stuck and the user experience will be extremely poor. This is not a joke. Therefore, pagination has become an optimization strategy that must be considered. After reading this article, you can not only learn how to implement the paging function, but also understand the performance optimization ideas behind it, avoiding falling into some common pitfalls.

Let’s talk about the basics first. el-cascader component of Element-UI does not support pagination itself. We have to do it ourselves and have enough food and clothing. This requires you to have a certain understanding of Vue's responsive mechanism, asynchronous data loading, and the API of Element-UI components. Of course, if you are not familiar with these, don't worry. I will try to explain in the most easy-to-understand way.

The core lies in how to load data asynchronously. We cannot load all data from the beginning, but gradually load the next level of data according to the user's choice. This requires a clever data structure and request strategy. I usually use an object to store all data, in the form of key-value pairs, the key is a parent ID and the value is an array of child data. For example:

 <code class="javascript">this.data = { '1': [ // 省份ID為1的市級(jí)數(shù)據(jù){ value: '101', label: '市A' }, { value: '102', label: '市B' }, // ... ], '101': [ // 市A的區(qū)縣數(shù)據(jù){ value: '10101', label: '區(qū)縣A1' }, { value: '10102', label: '區(qū)縣A2' }, // ... ], // ... };</code>

Then, in the load method of el-cascader , the server is requested asynchronously to obtain the corresponding data based on the currently selected node ID. Here, the key to pagination is this asynchronous request:

 <code class="javascript">load(node, resolve) { const { value } = node; const pageSize = 20; // 每頁顯示20條數(shù)據(jù)const currentPage = node.currentPage || 1; // 當(dāng)前頁碼this.$axios.get('/api/data', { params: { parentId: value, page: currentPage, pageSize } }) .then(response => { const { data, total } = response; node.total = total; // 更新總數(shù)據(jù)量，用于分頁組件resolve(data); }) .catch(error => { console.error(error); resolve([]); // 請(qǐng)求失敗，返回空數(shù)組}); }</code>

Have you noticed pageSize and currentPage parameters? This is the essence of pagination. The server needs to return the paged data according to these parameters and return the total data amount total so that the front-end can display the paged component.

Next, we need a pagination component. el-pagination component that comes with Element-UI is very suitable for this scenario. You just need to dynamically update the properties of the pagination component according to node.total .

Advanced usage? You can consider using virtual scrolling technology to further improve performance, especially when the amount of data is extremely large, virtual scrolling can avoid rendering all data and only rendering data in the currently visible area, which is a huge improvement in performance. Of course, implementing virtual scrolling requires more code and skills, so I won’t go into details here.

Common errors? The most common error is to forget to handle asynchronous requests, which causes the page to get stuck or display error messages. Be sure to properly handle the errors of asynchronous requests and give user-friendly prompts. There is also the transmission and processing of paging parameters. If you are not careful, it will lead to data display errors. Be sure to check your code carefully to ensure the correctness of the paging parameters.

Performance optimization? In addition to paging and virtual scrolling, data caching can also be considered to reduce unnecessary network requests. Rationally designing data structures and avoiding redundant data is also the key to improving performance. Code readability is also important, and clear and easy-to-understand code is easier to maintain and optimize.

In short, Vue and Element-UI cascaded drop-down box pagination is a problem that requires comprehensive consideration of performance and user experience. There is no perfect solution, only the best choice after weighing the pros and cons. Hope this article helps you better understand and solve this problem. Remember, code is just a tool, and more importantly, your understanding of the problem and your thinking on solving the problem. Only by practicing and thinking more can you become a real programming master!

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