How do you handle query parameters in Node.js?

Query parameters are commonly used in HTTP requests to pass data to the server as part of the URL. In Node.js, handling query parameters involves extracting and parsing query strings from request URLs to access parameter values and process them accordingly. Here’s how you can handle query parameters in Node.js:

• Using the URL Module:

• • • Parse query parameters from request URLs using the built-in URL module in Node.js. The URL module provides the URLSearchParams class for working with query strings and extracting parameter values
  • Example:

• javascript

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const { URLSearchParams } = require('url');

const url = require('url');




// Extract query parameters from request URL

const requestUrl = 'http://example.com/api/data?param1=value1&param2=value2';

const parsedUrl = new URL(requestUrl);

const queryParams = parsedUrl.searchParams;




// Access individual query parameters

const param1Value = queryParams.get('param1');

const param2

Value = queryParams.get('param2');

• Using Express.js:

• • • If you’re using Express.js, query parameters are automatically parsed and made available through the req.query object. Express parses the URL-encoded query string from the req.url property and populates req.query with an object containing the parsed query parameters.
  • Example:

• javascript

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const express = require('express');

const app = express();




// Route handler to handle requests with query parameters

app.get('/api/data', (req, res) => {

 const param1Value = req.query.param1;

 const param2Value = req.query.param2;

 res.json({ param1: param1Value, param2: param2Value });

});




app.listen(3000, () => {

 console.log('Server is running on port 3000');

});

• Parsing Query Strings Manually:

• • • In vanilla Node.js HTTP servers, you can manually parse query parameters from the request URL using the querystring module. This module provides utility functions for parsing and formatting URL query strings.
  • Example:

• javascript

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const http = require('http');

const querystring = require('querystring');




const server = http.createServer((req, res) => {

 const queryString = req.url.split('?')[1];

 const queryParams = querystring.parse(queryString);

 const param1Value = queryParams.param1;

 const param2Value = queryParams.param2;

 res.end(JSON.stringify({ param1: param1Value, param2: param2Value }));

});




server.listen(3000, () => {

 console.log('Server is running on port 3000');

});

• Handling Optional Parameters:

• • • Handle optional query parameters gracefully by checking if they exist before accessing their values. Use default values or fallbacks for optional parameters that are not provided in the request URL.
  • Example:

• javascript

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const param1Value = req.query.param1 || 'default';

const param2Value = req.query.param2 || null;

• Sanitizing and Validating Parameters:

• • • Validate and sanitize query parameters to ensure data integrity, prevent injection attacks, and handle unexpected input gracefully. Use validation libraries or custom validation logic to sanitize and validate parameter values before processing them.
  • Example:

• javascript

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const { sanitizeQuery } = require('express-validator');




app.get('/api/data', sanitizeQuery(['param1', 'param2']), (req, res) => {

 // Process sanitized query parameters

});

By handling query parameters effectively in Node.js applications, you can extract parameter values from request URLs, process them securely, and use them to customize request handling, data retrieval, and response generation based on client requirements.