Instruction: Discuss the process of implementing middleware in Next.js and how it can be used to modify responses or request objects.
Context: This question examines the candidate's understanding of Next.js middleware, its capabilities, and practical applications within a Next.js application.
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First, let me clarify that middleware in the context of Next.js serves as a function that runs before a request is completed. It allows us to intercept and modify the request and response objects, an ability that's crucial in implementing authentication, redirections, and custom headers, among other functionalities.
To implement middleware in a Next.js application, one typically starts by creating a file named _middleware.js within the pages or API routes directory where you intend to apply the middleware logic. This placement is strategic, as Next.js allows middleware to run at both the page and the route level, providing a versatile approach to handling requests....