Creating Reactive Applications with Vue.js

1. Introduction

This tutorial will guide you on how to make your Vue.js applications reactive. Vue.js is known for its efficient reactivity system, which allows updates to the user interface every time the data changes. By the end of this tutorial, you will have a good understanding of how to create Vue.js applications that are responsive to changes in data.

You will learn:

• The basic concepts of Vue.js reactivity
• How to create a reactive data object in Vue.js
• How to use watchers and computed properties

Prerequisites:

• Basic knowledge of JavaScript
• Familiarity with Vue.js is beneficial but not mandatory

2. Step-by-Step Guide

Vue.js Reactivity

Vue.js uses a "reactive data model". This means that whenever you change a data property in your Vue instance, Vue will automatically update all parts of your application where that data is being used.

Creating a Reactive Data Object

In Vue.js, the data object is the heart of every Vue instance. The data object is where you define properties that will be reactive.

var vm = new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue!'
  }
})

In the above code, message is a reactive property. If you change its value, Vue will reflect the changes in the UI.

Using Watchers and Computed Properties

Watchers and computed properties are powerful features in Vue.js that let you control how your data reacts to changes.

A watcher is a special Vue.js feature that listens to changes on your Vue instance's data. When the data changes, the watcher function is triggered.

Computed properties are similar to watchers, but they cache their results and only recompute when needed.

3. Code Examples

Example 1: A Basic Reactive Data Object

var vm = new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue!'
  }
})

// Change the value of message
vm.message = 'Hello World!'

/* 
Upon changing the `message` value, Vue.js automatically updates every place in your application where `message` is being used.
*/

Example 2: Using a Watcher

var vm = new Vue({
  el: '#app',
  data: {
    message: 'Hello Vue!'
  },
  watch: {
    message: function (newVal, oldVal) {
      console.log('message changed from ' + oldVal + ' to ' + newVal)
    }
  }
})

// Trigger the watcher by changing the value of message
vm.message = 'Hello World!'

Example 3: Using a Computed Property

var vm = new Vue({
  el: '#app',
  data: {
    firstName: 'John',
    lastName: 'Doe'
  },
  computed: {
    fullName: function () {
      return this.firstName + ' ' + this.lastName
    }
  }
})

console.log(vm.fullName) // "John Doe"

4. Summary

In this tutorial, we have covered the basics of creating reactive applications in Vue.js. We learned about Vue.js reactivity, how to create a reactive data object, and how to use watchers and computed properties.

Next, you could dive deeper into Vue.js by learning about components, Vue Router for routing, and Vuex for state management.

5. Practice Exercises

1. Create a Vue instance with a reactive data property. Change the value of the property and observe the effect on your application.

2. Add a watcher to a data property in your Vue instance. Make sure the watcher function logs a message to the console every time the property changes.

3. Use a computed property to create a full name from first and last name data properties. Change the values of the first and last name properties and observe the effect on the full name.

Solutions:

1. This exercise should be straightforward if you've followed the tutorial. Remember that you need to create a new Vue instance and define your data properties in the data object.

2. For this exercise, remember to define your watcher in the watch object of your Vue instance. The watcher function should take two arguments: the new value and the old value.

3. Remember that computed properties are defined in the computed object of your Vue instance. Use the this keyword to access your instance's data properties inside the computed property function.

Happy coding!