"Patience is key when it comes to waiting for components to render

Question

"Patience is key when it comes to waiting for components to render

Short Overview of the Issue

I'm currently exploring methods to access an onRendered lifecycle hook.

Finding on the Topic

A similar query was posted here: Vue $nextTick in mounted() hook doesn't work as expected

The explanation provided suggests that Vue processes reactive changes collectively per tick instead of rendering them directly. To ensure that subsequent changes are rendered after the next tick, developers can utilize the nextTick function.

By using the onMounted lifecycle hook, a user ensures that the component is mounted before making style alterations and waiting for the next tick to confirm the rendering of these adjustments. Despite this approach, the final 'state' is rendered immediately.

Although changes may occur so rapidly that they appear seamless, if noticeable, CSS transitions would be activated.

Suggested Resolution: Rather than awaiting the next tick, introducing an imperceptible delay (even 0ms) following the initial styling application appears to resolve the issue.

Rationale Behind My Insights

The documentation outlines that nextTick pertains to reactive state modifications; however, in this scenario, these involve styles which should result in direct DOM manipulation beyond Vue's purview... or does it?

In regards to the onMounted lifecycle hook explained in the documentation, although no clear assurance is given regarding when a component has been rendered, the statement reads:

This hook is typically used for performing side effects that need access to the component's rendered DOM ...

Hence, any stylistic changes within the onMounted block should ideally trigger immediate rendering and consequently activate the CSS transition, contrary to the observed behavior.

You can access a SFC Playground Demo showcasing the issue alongside the suggested "fix." The App.vue file solely handles component reloading without refreshing the page.

I harbor reservations towards the proposed solution as it relies on timely page loading or swift element rendering. These conditions could introduce challenges under heavy loads, alluding to a potential race condition where a minimal delay of 0ms fails to ensure consistent functionality across all page loads.

I'm seeking a reliable solution (or at best, a workaround) not contingent on chance occurrences. Furthermore, I am eager to delve deeper into the underlying causes behind the aforementioned behaviors.

javascript vue.js vuejs3 vue-component

Answer 1

Answer №1

I found a great explanation comparing nextTick() and setTimeout().

In my opinion, if you want a more reliable solution, using setTimeout() would be the way to go. Alternatively, consider taking a different approach by utilizing Vue's built-in Transition component.

<Transition name="slide" appear>
  <div ref="blockRef" class="block"></div>
</Transition>

The use of the appear property will initiate the transition upon initial rendering.

Here is the CSS for the slide transition:

.block {
    ...
    top: 26vh  /* specifies the end state of the transition */
}

.slide-enter-active {
    transition: top 3s linear 0s
}
.slide-enter-from {
    top: 0
}
.slide-enter-to {
    top: 26vh
}

If the transition works on mount, remounting the component will essentially restart it. Changing the key value can achieve this effectively.

App.vue

const myRef = ref(true);
async function restart() {
  myRef.value = !myRef.value
}

<button @click="restart">Restart</button>
<Comp :key="String(myRef)" />

Try out Vue Playground

Answer 2

I found a great explanation comparing nextTick() and setTimeout().

In my opinion, if you want a more reliable solution, using setTimeout() would be the way to go. Alternatively, consider taking a different approach by utilizing Vue's built-in Transition component.

<Transition name="slide" appear>
  <div ref="blockRef" class="block"></div>
</Transition>

The use of the appear property will initiate the transition upon initial rendering.

Here is the CSS for the slide transition:

.block {
    ...
    top: 26vh  /* specifies the end state of the transition */
}

.slide-enter-active {
    transition: top 3s linear 0s
}
.slide-enter-from {
    top: 0
}
.slide-enter-to {
    top: 26vh
}

If the transition works on mount, remounting the component will essentially restart it. Changing the key value can achieve this effectively.

App.vue

const myRef = ref(true);
async function restart() {
  myRef.value = !myRef.value
}

<button @click="restart">Restart</button>
<Comp :key="String(myRef)" />

Try out Vue Playground

"Patience is key when it comes to waiting for components to render

Short Overview of the Issue

Finding on the Topic

Rationale Behind My Insights

Answer №1

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