Day 8: Vue.js Watchers and Lifecycle Methods

Table of Contents

• Understanding Watchers: Their Purpose and How to Create Them
• Overview of Lifecycle Methods in Vue.js

On Day 8, we’ll explore watchers and lifecycle methods in Vue.js. Understanding these concepts will give you greater control over how your Vue.js applications behave and respond to changes.

Understanding Watchers: Their Purpose and How to Create Them

In Vue.js, a watcher is a special type of Vue instance property that allows you to watch for changes on your Vue instance’s data properties. When a watched data property changes, a function that you provide gets executed. This function can then perform any side effects that are necessary in response to the data change.

Here’s an example of a watcher:

new Vue({
  el: '#app',
  data: {
    message: 'Hello, Vue!'
  },
  watch: {
    message: function(newValue, oldValue) {
      console.log('The message property changed from ' + oldValue + ' to ' + newValue);
    }
  }
})

In this example, we create a watcher on the message data property. Whenever message changes, the function we provided in the watcher gets called, and the old and new values of message get logged to the console.

Overview of Lifecycle Methods in Vue.js

Lifecycle methods are special methods that Vue.js calls at different stages of a Vue instance’s life, from creation to destruction. They give you hooks where you can add code that should run when specific events occur in the life of your Vue instances or components.

The lifecycle methods in Vue.js are:

• beforeCreate: Called before the Vue instance has been created.
• created: Called after the Vue instance has been created.
• beforeMount: Called before the Vue instance is mounted onto the DOM.
• mounted: Called after the Vue instance has been mounted onto the DOM.
• beforeUpdate: Called before the Vue instance updates.
• updated: Called after the Vue instance updates.
• beforeDestroy: Called before the Vue instance is destroyed.
• destroyed: Called after the Vue instance is destroyed.

By understanding and correctly utilizing watchers and lifecycle methods, you can create more efficient and responsive Vue.js applications. We’ll dive deeper into these topics in future lessons.

That’s it for today! Tomorrow, we’ll explore components in Vue.js, the building blocks of Vue applications. Stay tuned!