How to persist data in React.js and Next.js | learn Data Persistence in Javascript and React

Summary

In this tutorial, the speaker explains data persistence in a Next.js weather app, focusing on how to store and retrieve user preferences (e.g., Imperial or Metric units) using local storage. The video covers various data persistence methods, including local storage, server-side rendering, client-side APIs, cookies, and state management libraries. The primary focus is on local storage, where user settings are saved, ensuring preferences are remembered even after closing and reopening the browser. The tutorial provides hands-on examples of using JavaScript to manage and persist data with local storage, emphasizing practical implementation in web applications.

Takeaways

• 😀 Data persistence ensures that data remains accessible even after an application stops running.
• 😀 A real-life example of data persistence is when an online store remembers items in your cart, even if you close the browser.
• 😀 There are several methods for persisting data, including local storage, server-side rendering with a database, cookies, and client-side APIs.
• 😀 Local storage allows data to be stored in the browser as key-value pairs but can be lost if the browser cache is cleared.
• 😀 Server-side rendering (SSR) with a database stores data on a server, ensuring it’s available across devices and isn’t lost when clearing browser data.
• 😀 Using cookies allows data to be stored with an expiration date, which can help persist data for a specified period.
• 😀 State management libraries like Redux can store data centrally, but they may not be ideal for simpler applications.
• 😀 Third-party services like Firebase or AWS offer easy ways to persist data without the need for setting up a server or database.
• 😀 Local storage is useful for storing non-essential data like user preferences (e.g., theme or units) rather than sensitive information.
• 😀 The `setItem` and `getItem` methods are used to interact with local storage, with the data being stored as strings.
• 😀 When storing non-string data (like objects or booleans), it should be stringified using `JSON.stringify()` before saving and parsed using `JSON.parse()` when retrieving.

Q & A

What does 'data persistence' mean in the context of a web application?

Data persistence refers to the ability of a web application to store and retrieve data even after the application or browser has stopped running. It ensures that data is not lost when the application is closed or refreshed.

Can you give an example of data persistence from everyday use?

A common example is when you add items to a shopping cart on websites like Amazon or eBay. If you accidentally close your browser or log out, the items remain in the cart when you log back in, which is a form of data persistence.

What are some methods to persist data in a Next.js application?

Some methods to persist data in Next.js applications include using local storage, server-side rendering with a database, client-side rendering with an API, cookies, state management libraries like Redux or MobX, and third-party services like Firebase or AWS.

Why did the tutorial choose to use local storage to persist data in the weather app?

Local storage was chosen because the data being persisted (user preferences like imperial or metric units) is non-essential. It doesn't involve sensitive or critical information, and local storage is simple and sufficient for this use case.

What is the limitation of using local storage for data persistence?

The main limitation of using local storage is that the data is tied to the browser. If the user clears their cache or cookies, the data will be lost. Additionally, local storage is only accessible on the device where the data was stored.

What are the advantages of using server-side rendering (SSR) with a database for data persistence?

SSR with a database ensures that data is stored on a server and can be accessed from any device. It is more persistent than local storage because data remains available even if the user clears their browser's cache or cookies.

How do cookies help with data persistence, and how are they different from local storage?

Cookies are small pieces of data stored in a user's browser that can be accessed by both the client and the server. They have an expiration date, so they can store data for a specific period, unlike local storage, which persists until manually cleared.

What is the significance of using JSON.stringify and JSON.parse with local storage?

When storing complex data like objects or arrays in local storage, you need to use JSON.stringify to convert them into a string format. When retrieving the data, JSON.parse is used to convert it back into its original format, such as an object or array.

What role does the useEffect hook play in the weather app for data persistence?

The useEffect hook is used to check if there is any persisted data (like the imperial or metric units) in local storage when the user opens the app. If data exists, it is retrieved and set as the initial value for the units; if no data is found, the app loads with default settings.

How does the toggle switch for changing units (imperial/metric) work with local storage in the app?

The toggle switch updates the value in local storage whenever the user switches between imperial and metric units. This value is saved using local storage's setItem method, and the app retrieves it upon reopening, ensuring the units are preserved across sessions.