As the development of Internet technology continues to deepen, front-end technology is also constantly being upgraded and iterated. Among them, Vue, as one of the most popular MVVM frameworks at present, has been favored by more and more developers. In the daily development process, data changes are often involved, and Vue can update views in real time through a data responsive system. However, when the amount of data is large, full update will have an impact on performance, and incremental update technology needs to be used in this case.
1. What is incremental update?
Incremental update refers to updating only the parts that need to be updated while keeping the current view unchanged. For example, if a page has 1,000 pieces of data and one piece of data changes, if you use the full update method, you need to re-render the entire page; if you use the incremental update method, you only need to update the changed data. Can.
2. Why is incremental update needed?
As mentioned above, the full update method will have an impact on performance, especially when the amount of data in the page is very large. Incremental updates can reduce unnecessary operations, improve web page performance, and enhance user experience.
3. How does Vue implement incremental updates?
Vue.mixin is a function that can globally mix Vue options or components. By using Vue.mixin, we can use the $forceUpdate() method in the template to force component changes to be updated. However, using $forceUpdate() will cause all data in the component to be fully updated instead of incrementally. So we need a more reasonable approach.
Vue.set is used to add new elements to an object or array and is an important API provided by Vue. Vue.set can also automatically trigger the operation of updating the view while adding elements. It is a method to achieve incremental updates.
Vue.set(object, key, value) Vue.set(array, index, value)
Parameter description:
The computed property is a commonly used calculated property in Vue. It is cached based on reactive dependencies and will only be recalculated when the value of the calculated property dependency changes. By monitoring dependencies in the computed attribute, we can achieve incremental updates of data.
computed: {
filteredData() {
return this.data.filter(item => item.price > 100)
}
}In the above code, when the price of an item in the data changes, the filteredData in the computed attribute will be automatically updated, and only the changed items will be updated, achieving the effect of incremental update.
v-for is a commonly used loop instruction in Vue. It can traverse each element in an array or object in sequence and perform corresponding operate. When using v-for, if you do not add a unique key value to each item, Vue will try to use the index as the key by default. But when an item of data in the array or object changes, Vue cannot correctly determine which item has changed, so it can only perform a full update, which affects performance. Adding a unique key value to each item can accurately identify changed items, thereby enabling incremental updates.
<div v-for="(item, idx) in items" :key="item.id">
<span>{{ item.name }}</span>
<span>{{ item.price }}</span>
</div>By adding a unique key value to each item in v-for, the changed items can be accurately identified, thereby achieving the effect of incremental updates.
Summary:
Incremental update is one of the important means to achieve high-performance applications. Vue, as one of the most popular MVVM frameworks at present, also provides a variety of methods to implement incremental updates. . By combining methods such as Vue.set, computed attributes, and keys in v-for, we can update data more efficiently, improve application performance, and enhance user experience.
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