Watchers in Vue 3: A Comprehensive Guide

In Vue 3, watchers are a powerful tool for building dynamic and reactive user interfaces. Watchers allow you to watch for changes in data properties, and perform tasks when the data changes. In this tutorial, we'll take a look at how to use watchers in Vue 3 to build reactive and efficient UIs.

To define a watcher in Vue 3, you can use the watch option in the component's options object. The watch option is an object that contains the data properties you want to watch, and the corresponding callback function for each property.

For example, let's say you have a data property called searchTerm, and you want to perform a search when the searchTerm property changes:

  <input v-model="searchTerm">

export default {
  data() {
    return {
      searchTerm: '',
  watch: {
    searchTerm(newValue, oldValue) {
      console.log(`Search term changed from "${oldValue}" to "${newValue}"`);
  methods: {
    performSearch() {
      // perform the search here

In this example, the searchTerm watcher is defined in the watch option, and the callback function is called whenever the searchTerm property changes. The callback function receives the new value and the old value of the searchTerm property as arguments, and logs a message to the console. The callback function also calls the performSearch method, which performs the actual search.

By using watchers, you can build dynamic and reactive UIs that can adapt to changing data states and user input. For example, you can use watchers to trigger updates when data properties change, or to perform actions based on user input.

Whether you're building a simple form or a complex single-page application, watchers are a key tool for building dynamic and reactive UIs with Vue 3. By learning how to use watchers effectively, you can build responsive and interactive UIs that can adapt to changing data states and user input.