What is nextTick and what does it do in Vue.js?

In Vue.js, the nextTick method is used to schedule a callback to be executed after the next DOM update cycle.

It allows you to perform operations after the Vue instance has finished updating the DOM, ensuring that you’re working with the latest changes. This is particularly useful when you want to manipulate the DOM or access the updated values immediately after a data change.

Here’s an example to illustrate the use case of nextTick in Vue.js:

<template>
  <div>
    <p>{{ message }}</p>
    <button @click="updateMessage">Update Message</button>
  </div>
</template>


<script>
export default {
  data() {
    return {
      message: "Initial message"
    };
  },
  methods: {
    updateMessage() {
      this.message = "New message"; // Update the data property
      const paragraph = document.querySelector('p');
      console.log(paragraph.textContent); // Outputs: Initial message
    }
  }
};
</script>

In the above example, we have a Vue component with a message data property. When the “Update Message” button is clicked, the updateMessage method is called, which updates the message property with a new value.

But when we try to access an element using document.querySelector(), We are getting an old value because Vue hasn’t finished updating the DOM.

Here’s an example how to get updated DOM result using nextTick:

<template>
  <div>
    <p>{{ message }}</p>
    <button @click="updateMessage">Update Message</button>
  </div>
</template>


<script>
export default {
  data() {
    return {
      message: "Initial message"
    };
  },
  methods: {
    updateMessage() {
      this.message = "New message"; // Update the data property


      this.$nextTick(() => {
        // This callback will be executed after the next DOM update cycle
        // Accessing the DOM or data here ensures that it reflects the latest changes


        const paragraph = document.querySelector('p');
        console.log(paragraph.textContent); // Outputs: New message
      });
    }
  }
};
</script>

In the above example, Immediately after updating the data property, this.$nextTick() is called with a callback function. Inside the callback, we access the DOM to get the text content of the < p > element, which displays the message value. Since this.$nextTick() ensures that the DOM has been updated with the latest changes, we can be sure that the text content will reflect the updated value of the message.