Understanding window.location.pathname Error in React and Next.js

Описание: Explore why `window.location.pathname` may lead to a ReferenceError in one function while working seamlessly in another. Learn the proper way to handle routing in Next.js.
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This video is based on the question https://stackoverflow.com/q/65417440/ asked by the user 'Justin Blayney' ( https://stackoverflow.com/u/5200574/ ) and on the answer https://stackoverflow.com/a/65442722/ provided by the user 'Justin Blayney' ( https://stackoverflow.com/u/5200574/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Understanding window.location.pathname Error in React and Next.js: A Complete Guide

When developing web applications with frameworks like React and Next.js, you might run into some perplexing issues, especially around routing. One common issue developers face is when window.location.pathname works in one function but throws an error in another function. This post will break down this problem, explore why it's happening, and guide you towards the correct solution.

The Problem: window.location.pathname ReferenceError

You may have encountered an error message similar to this:

[[See Video to Reveal this Text or Code Snippet]]

This usually indicates that the code is being executed in an environment where the window object is not available. In React apps, the window object is only accessible in the browser and not during server-side rendering (SSR). Let's break down the specifics.

The Code Snippet

Here’s the code where you might see the issue arise:

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In this code, the goal is to retrieve the current path of the application and display it in the console. But when executed outside of a client-side context (like during SSR in Next.js), this can trigger the ReferenceError since window does not exist on the server.

Why Does It Work in One Function but Not Another?

The discrepancy arises due to the context in which each function is executed. If the error occurs in a certain function, yet similar code works perfectly in another function, the solution goes back to whether that function is executed on the server or client side.

Server-Side Rendering (SSR) vs. Client-Side Rendering (CSR)

Server-Side Rendering (SSR):

Executes code on the server before sending the fully rendered page to the client.

The window object is not defined, resulting in error messages like the one mentioned above.

Client-Side Rendering (CSR):

Once the page reaches the client, scripts can access browser-specific objects, including window.

Here, window.location.pathname would function correctly.

How to Handle Routing in Next.js Properly

Instead of relying directly on window.location.pathname, Next.js provides a built-in way to access routing information using the useRouter hook. Here’s how you can implement it:

Step 1: Import useRouter

Import the useRouter hook from Next.js.

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Step 2: Use the router Object

You can use the router object to safely access the pathname without encountering the ReferenceError.

[[See Video to Reveal this Text or Code Snippet]]

router.pathname will give you the current path, whether you are on the client or server.

Conclusion

Understanding the discrepancies between client-side and server-side execution is crucial when working with frameworks like Next.js. By replacing window.location.pathname with Next.js's useRouter, you can manage page routing effectively without running into common pitfalls. Remember, making the right adjustments based on your application's execution context can save you a lot of debugging time and headaches.

Now that you have a clearer understanding, you can confidently navigate routing in your Next.js applications and avoid those pesky ReferenceError messages.