Managing State in Nuxt.js

1. Introduction

In this tutorial, we're going to learn about managing state in Nuxt.js using Vuex. State management is an essential part of any non-trivial Nuxt.js application. By the end of this tutorial, you will understand how to manage and manipulate state in your Nuxt.js applications.

You will learn:
- How to create and structure your Vuex store.
- How to define state, mutations, actions, and getters.
- How to access state in your components.

Prerequisites:
- Basic knowledge of JavaScript.
- Basic understanding of Vue.js and Nuxt.js.
- Basic understanding of Vuex.

2. Step-by-Step Guide

Vuex Store:
In Nuxt.js, each .js file inside the store directory is transformed as a namespaced module (index being the root module). Your store structure should be:

store/
--| user.js
--| index.js

State: The state is where we will store our app-level data. Here's how you can define a state in your Vuex store.

export const state = () => ({
  counter: 0
})

Mutations: Mutations are functions that directly manipulate the state. Mutations should always be synchronous.

export const mutations = {
  increment (state) {
    state.counter++
  }
}

Actions: Actions are similar to mutations, but they commit mutations and can contain arbitrary asynchronous operations.

export const actions = {
  increment (context) {
    context.commit('increment')
  }
}

Getters: Getters are functions that compute derived state based on your store state.

export const getters = {
  counter: state => state.counter
}

Accessing State in components: You can access your state data in your components using this.$store.state.<moduleName>.<stateName>.

computed: {
  counter () {
    return this.$store.state.counter
  }
}

3. Code Examples

Example 1: Counter Module

This is a simple counter module with a mutation to increment the counter.

// ~/store/counter.js

export const state = () => ({
  count: 0
})

export const mutations = {
  increment (state) {
    // increment counter by one
    state.count++
  }
}

Example 2: Accessing counter in a component

This is an example of how to access the counter state in a Nuxt.js component.

<template>
  <div>
    <button @click="incrementCounter">Increment</button>
    <p>Counter: {{ counter }}</p>
  </div>
</template>

<script>
export default {
  computed: {
    counter() {
      // access the counter state
      return this.$store.state.counter.count
    }
  },
  methods: {
    incrementCounter() {
      // commit the increment mutation
      this.$store.commit('counter/increment')
    }
  }
}
</script>

4. Summary

You've learned how to manage state in Nuxt.js applications using Vuex. You've seen how to define a state, commit mutations, dispatch actions, and get state in your components. You've also learned how to structure your Vuex store, and the difference between state, mutations, actions, and getters.

To continue learning, you should read the official Nuxt.js docs and the Vuex docs. You should also build your own Nuxt.js applications and practice managing state with Vuex.

5. Practice Exercises

Exercise 1: Create a Vuex module for managing todos with actions for adding, deleting, and toggling todos.

Exercise 2: Create a Nuxt.js component that displays the todos and has buttons for adding, deleting, and toggling todos.

Exercise 3: Modify the todos module to save the todos in local storage, so they persist when the page is refreshed.

Tips: Remember to use mutations to change state, and actions to commit mutations. Use computed properties to access state in your components.