Avoiding unnecessary DOM updates in VueJS

Question

Avoiding unnecessary DOM updates in VueJS

Implementing an animated carousel has been my latest project, and I've been using code similar to the following:

<template>
<div v-for="(slides, id)" v-if="id > middle_id - 2 || id < middle_id + 2">
<div :class="'slide'+id"><slide :key="id" :slide-data="slide" /></div>
</div>
</template>

The number of slides can vary, but only the middle 5 are shown. The animations rely on css animation properties, which are based on the slide number.

This setup works smoothly if I add or remove slides individually - the existing DOM elements remain unchanged and only one new slide is introduced. However, when I simultaneously add a slide to the end and remove one from the beginning, Vue seems to re-render all of the DOM elements in the sliding window.

I'm wondering if there's a way to ensure that during this process, the 3 middle slides that haven't changed are not updated in the DOM?

javascript vue.js dom

Answer 1

Answer №1

Vue 3.2 and Above

If you are using Vue versions 3.2 or higher, you can achieve this functionality by utilizing the v-memo directive.

<div v-memo="[itemA, itemB]">
  ...
</div>
Whenever the component is re-rendered, if both itemA and itemB retain their values, all updates for this element and its descendants will be omitted. In fact, the creation of Virtual DOM VNodes will also be skipped because the memoized version of the subtree can be recycled.

Explore more about v-memo in the official Vue documentation

Answer 2

Vue 3.2 and Above

If you are using Vue versions 3.2 or higher, you can achieve this functionality by utilizing the v-memo directive.

<div v-memo="[itemA, itemB]">
  ...
</div>
Whenever the component is re-rendered, if both itemA and itemB retain their values, all updates for this element and its descendants will be omitted. In fact, the creation of Virtual DOM VNodes will also be skipped because the memoized version of the subtree can be recycled.

Explore more about v-memo in the official Vue documentation

Answer 3

Answer №2

While working with Vue to create a carousel text feature, I came across a similar issue and managed to find an effective solution for it.

Vue includes specific rules in its source code to determine when to recycle DOM elements in various situations. Essentially, Vue does not recycle DOM elements when:

a single node is removed,
a single node is added, or
the attributes of a node are modified.

The problem arises when you both add and remove slides in one step. Vue does not immediately update the DOM elements if you add a slide and then remove another in quick succession.

Vue updates the DOM asynchronously, consolidating multiple data modifications into one before updating the DOM. To ensure that adding and removing slides are treated as separate actions, using await Vue.nextTick() (or await this.$nextTick()) can be quite effective. This ensures that the code below will only execute once the DOM has been updated.

To implement this solution, you can refer to the following example code snippet:

async function updateSlides() {
    // Add a new slide to the array
    this.arr.push({ ... })

    // Wait for the DOM update to happen
    await this.$nextTick()

    // Remove the first slide from the array
    this.arr.splice(0, 1)
}

Following these steps should help you achieve your desired result and effectively resolve the issue at hand.

Answer 4

While working with Vue to create a carousel text feature, I came across a similar issue and managed to find an effective solution for it.

Vue includes specific rules in its source code to determine when to recycle DOM elements in various situations. Essentially, Vue does not recycle DOM elements when:

a single node is removed,
a single node is added, or
the attributes of a node are modified.

The problem arises when you both add and remove slides in one step. Vue does not immediately update the DOM elements if you add a slide and then remove another in quick succession.

Vue updates the DOM asynchronously, consolidating multiple data modifications into one before updating the DOM. To ensure that adding and removing slides are treated as separate actions, using await Vue.nextTick() (or await this.$nextTick()) can be quite effective. This ensures that the code below will only execute once the DOM has been updated.

To implement this solution, you can refer to the following example code snippet:

async function updateSlides() {
    // Add a new slide to the array
    this.arr.push({ ... })

    // Wait for the DOM update to happen
    await this.$nextTick()

    // Remove the first slide from the array
    this.arr.splice(0, 1)
}

Following these steps should help you achieve your desired result and effectively resolve the issue at hand.

Avoiding unnecessary DOM updates in VueJS

Answer №1

Vue 3.2 and Above

Answer №2

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