TanStack Query is a powerful data-fetching and server-state management library that supports multiple frameworks such as React, Vue, Solid, Svelte, and vanilla JavaScript. It is designed to simplify data synchronization between your UI and remote data sources, making fetching, caching, and updating data a breeze.

Why TanStack Query? 🌟

TanStack Query offers a range of features that address common challenges in data-fetching:

1. Automatic Caching: It caches requests to avoid redundant network calls.
2. Background Refetching: Keeps data up-to-date without blocking the UI.
3. Automatic Synchronization: Reacts to changes like focus, connectivity, or interval updates.
4. Error Handling: Built-in tools to manage errors, retries, and timeouts.
5. Mutations: Optimistic updates and invalidation for handling data changes.
6. Pagination & Infinite Queries: Simplifies loading more data as needed.
7. SSR & ISR Support: Works seamlessly with server-side rendering (SSR) and incremental static regeneration (ISR).

Key Concepts 🧠

• Query: A piece of data that you can fetch and cache.
• Mutation: An operation that modifies data, such as a POST or DELETE request.
• Query Client: Manages the life-cycle of queries across your application.

Where Can You Use It? 🌐

TanStack Query can be used in various contexts:

• React, Vue, Solid, Svelte, Angular (experimental): TanStack integrates smoothly with these frameworks.
• Vanilla JS: Use it without any UI library.
• Server-Side Rendering (SSR): Handle data preloading for server-rendered apps.
• React Native and mobile apps: Manage state and server data with ease.

How TanStack Query Works 🛠️

Installation

To install TanStack Query, run the following command (for React):

          

            
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          npm install @tanstack/query-core

For other frameworks like Vue or Solid, replace query-core with vue-query, solid-query, etc.

Code Example: Fetching Data with TanStack Query

Here’s a generic example using the core API (applicable in vanilla JS):

1. Set up the QueryClient:

          

            
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          import { QueryClient } from '@tanstack/query-core';

const queryClient = new QueryClient();

2. Define a query:

This fetches a list of items from an API and caches the results.

          

            
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          queryClient.fetchQuery({
  queryKey: ['todos'],
  queryFn: () => fetch('/api/todos').then(res => res.json())
});

3. Access Cached Data:

After fetching, you can retrieve the cached data at any time.

          

            
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          const todos = queryClient.getQueryData(['todos']);
console.log(todos); // Displays cached todo data

4. Automatic Background Refetch:

TanStack Query will automatically refetch data in the background when conditions change (e.g., window refocus).

🔄 Handling Mutations

Mutations are crucial when you need to modify data on the server (e.g., submitting forms or updating a database). Here’s how you can implement a mutation using the core API:

          

            
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          // Define a mutation function to modify data
const mutateData = async (newData) => {
  const response = await fetch('https://api.example.com/data', {
    method: 'POST',
    body: JSON.stringify(newData),
  });
  if (!response.ok) throw new Error('Mutation failed');
  return response.json();
};

// Execute the mutation
queryClient.executeMutation({
  mutationFn: mutateData,
  variables: { id: 1, value: 'Updated Value' },
})
  .then(result => console.log('Mutation Result:', result))
  .catch(error => console.error('Mutation Error:', error));

📝 Key Points:

• Optimistic Updates: You can temporarily update the local state before the server responds, improving the user experience.
• Error Handling: Handle mutation errors gracefully to provide feedback to the user.
• Background Refetch: After a mutation, you can trigger background refetching to keep data in sync with the server.

🚀 Conclusion

TanStack Query is a robust solution for handling server-side state in any environment. With support for popular frameworks like React, Vue, Svelte, and Solid, and an easy-to-use core package, it’s a must-have in your toolbox for managing API calls and caching efficiently. Mutations, like queries, are simple yet powerful, providing an elegant way to handle server-side modifications with ease.