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Tanmay Gupta
Tanmay Gupta

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Working with Route Parameters and Query Strings in Express

#webdev #javascript #api #programming

When building web applications or APIs with Express.js, it's essential to understand how to work with route parameters and query strings. These two features allow your server to respond dynamically based on values sent in the URL.

In this post, you’ll learn:

  • What route parameters and query strings are
  • How to use them in Express
  • Real-world examples

What Are Route Parameters?

Route parameters are parts of the URL path that are treated as variables. They are defined using a colon (:).

Example:

GET /users/123
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In this case, 123 is a dynamic route parameter, typically representing a user ID.

How to Access Route Parameters in Express 

app.get('/users/:id', (req, res) => {
  const userId = req.params.id;
  res.send(`User ID is ${userId}`);
});
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If you visit http://localhost:3000/users/42, the server will respond with:

User ID is 42
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You can also have multiple parameters:

app.get('/users/:userId/posts/:postId', (req, res) => {
  const { userId, postId } = req.params;
  res.send(`User: ${userId}, Post: ${postId}`);
});
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What Are Query Strings?

Query strings are key-value pairs added to the end of a URL after a ?.

Example:

GET /search?term=express&page=2
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Here:

  • term=express
  • page=2

How to Access Query Strings in Express 

app.get('/search', (req, res) => {
  const { term, page } = req.query;
  res.send(`Searching for "${term}" on page ${page}`);
});
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If you visit http://localhost:3000/search?term=node&page=3, the response will be:

Searching for "node" on page 3
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Combining Both

You can use route parameters and query strings together.

Example:

app.get('/users/:id/details', (req, res) => {
  const userId = req.params.id;
  const { includePosts } = req.query;
  res.send(`User ID: ${userId}, Include Posts: ${includePosts}`);
});
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Visit:

http://localhost:3000/users/5/details?includePosts=true
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Response:

User ID: 5, Include Posts: true
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Use Cases

Feature Use Case Example
Route Parameters /products/:id for product details
Query Strings /products?category=books&sort=price

Summary

Feature Syntax Example Access in Express
Route Parameters /users/:id → /users/12 req.params.id
Query Strings /search?term=book&page=2 req.query.term, req.query.page

Understanding how to handle route parameters and query strings helps you build flexible, dynamic APIs and pages with Express.

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