What is Vue nextTick? Accessing the DOM after Data Updates

Vue's nextTick is a core function that helps manage the timing of DOM updates in Vue applications. It provides a way to execute code after Vue has finished updating the DOM, ensuring you're working with the latest rendered state.

How Vue Updates Work

Vue performs DOM updates asynchronously. When you change reactive data, Vue doesn't immediately update the DOM. Instead, it:

1. Batches multiple data changes into a single update
2. Places these updates in an async queue
3. Processes the queue on the next "tick" of the event loop

This optimization prevents unnecessary DOM updates and improves performance.

When to Use Vue nextTick

You need nextTick when:

• Accessing updated DOM elements immediately after changing data
• Performing operations that depend on the new DOM state
• Measuring updated element dimensions (for example clientWidth and clientHeight)
• Working with third-party libraries that manipulate the DOM (such as charts.js).

Practical Example of Vue nextTick for Auto Scrolling a List to the Bottom after Data Change

Let’s take a look at a practical example of when nextTick might be helpful. In the code below, we're adding items to a scrollable list. Without nextTick, attempting to scroll to the bottom immediately after adding an item wouldn't work but using nextTick ensures we access the correct scrollHeight after the DOM has been updated.

<script setup>
import { ref, nextTick } from 'vue';

const items = ref([]);
const newItem = ref('');
const itemsList = ref(null);

const addItem = async () => {
  // Add item to list
  items.value.push(newItem.value);
  newItem.value = '';

  // This won't work immediately
  console.log('before DOM Update', itemsList.value.scrollHeight);

  // Wait for DOM update
  await nextTick();

  // Now we can safely access the updated DOM
  const container = itemsList.value;
  container.scrollTop = container.scrollHeight;
  console.log('after DOM Update', itemsList.value.scrollHeight);
};
</script>

<template>
  <div>
    <div ref="itemsList" class="items-container">
      <div v-for="item in items" :key="item">
        {{ item }}
      </div>
    </div>

    <input v-model="newItem" @keyup.enter="addItem" />
    <button @click="addItem">Add Item</button>
  </div>
</template>

<style scoped>
.items-container {
  height: 50px;
  margin-bottom: 5px;
  border: 1px solid black;
  padding: 5px;
  overflow: scroll;
}
</style>

See the example in action in this StackBlitz playground. Try removing the nextTick to see what happens.

How to use Vue’s nextTick with the Composition API

nextTick must be imported from Vue and can be used in a couple different ways. Since it returns a promise you can await the promise resolution. You can use .then to call a function when the promise resolves. Finally, you could pass it a callback function as the only argument.

// Using nextTick imported from vue
import { nextTick } from 'vue'

// Promise syntax
await nextTick()
// DOM is now updated

// Alt promise syntax
nextTick().then(()=>{
  // DOM is now updated
})

// Callback syntax
nextTick(() => {
  // DOM is now updated
})

Common Gotchas When Using nextTick

While extremely handy, there are a couple common mistakes people make when using nextTick just like some other tools Vue provides.

1. Don't overuse nextTick - only use it when you actually need to access the updated DOM
2. nextTick doesn't guarantee third-party DOM changes are complete, only Vue's updates, so consult the thrid-party’s docs for info on any events they provide

Conclusion

While not a tool you reach for every day, understanding nextTick can help elevate your Vue development skills and open up more possibilities for good UX.