Question

How can I implement pagination for large datasets in an Express.js API?

I'm building an Express.js backend for my application and running into CORS (Cross-Origin Resource Sharing) issues when trying to access it from a frontend application. I need to understand how to properly configure my Express server to allow cross-origin requests. What are the best practices for handling CORS in Express.js, and how can I implement them to resolve these issues?

Answer 1

Pagination is a technique used to divide large datasets into smaller , more manageable pages. This prevents overwhelming the client with excessive data and improves performance.

Let’s see how to implement pagination :

1. Define Query Parameters :
- page : The current page number.
- limit : The number of items per page
2. Parse Query Parameters :
- Use req.query to access the query parameters from the incoming request.
- Parse and validate the values to ensure they are valid integers.
3. Calculate Offset :
- The offset is the starting index for the current page.
- Calculate it using the formula : offset = (page - 1) * limit
4. Query the Database :
- Use your database library(e.g., Mongoose) to query the data.
- Apply the offset and limit to the query to retrieve the desired subset of data
5. Return the Response :
- Include the paginated data , total pages , current page , and items per page in the response.