1. Introduction

The goal of this tutorial is to help you understand the 'context' object in Nuxt.js middleware. Middleware in Nuxt.js allows you to define custom functions that can run before rendering either a page or a group of pages. The 'context' object is a powerful feature that provides access to key aspects of your application.

By the end of this tutorial, you will:

• Understand what the 'context' object is in Nuxt.js middleware
• Learn how to use the 'context' object in your Nuxt.js applications
• Gain practical experience with code examples

Prerequisites:

• Basic understanding of JavaScript
• Basic knowledge of Vue.js and Nuxt.js

2. Step-by-Step Guide

In Nuxt.js, middleware receives the context as the first argument. The context is a special object that contains a lot of useful properties and methods, such as params, query, req, res, store, redirect, etc.

export default function (context) {
  // Use context
}

Context is available in several places:
* In data and fetch method
* On the server-side in asyncData and nuxtServerInit
* In middleware

3. Code Examples

Here are some practical examples to help you understand the context object:

Example 1: Accessing route params in middleware

// middleware/checkParams.js
export default function (context) {
  // access route params
  const { params } = context
  console.log(params) // { id: '1' }
}

In this example, we create a middleware function checkParams that logs the route parameters. If we navigate to a route like /post/1, the console will output { id: '1' }.

Example 2: Using redirect method

// middleware/redirect.js
export default function (context) {
  // use redirect method
  if (!context.store.state.authenticated) {
    context.redirect('/login')
  }
}

In this example, we check if the user is authenticated. If not, we use the redirect method from the context object to navigate the user to the login page.

4. Summary

In this tutorial, we've covered:

• The basic understanding of the context object in Nuxt.js middleware
• How to use various properties of the context object
• Practical examples of using the context object in middleware

Next steps:

• Try to create your own middleware using different properties of the context object
• Understand how to use context in asyncData and nuxtServerInit

Additional resources:

• Nuxt.js Documentation - Context API

5. Practice Exercises

Exercise 1: Create a middleware function that logs the query parameters of the current route.

Solution:

// middleware/logQuery.js
export default function (context) {
  // log query parameters
  console.log(context.query)
}

Exercise 2: Create a middleware function that checks if a user is an admin. If not, redirect them to a '/no-access' page.

Solution:

// middleware/checkAdmin.js
export default function (context) {
  // check if user is an admin
  if (context.store.state.user.role !== 'admin') {
    context.redirect('/no-access')
  }
}

These exercises should give you some practical experience with using the context object in Nuxt.js middleware. Keep practicing to improve your understanding.