How to handle URL parameters in Express ?

In this article, we will discuss how to handle URL parameters in Express. URL parameters are a way to send any data embedded within the URL sent to the server. In general, it is done in two different ways.

Steps to Create Express Application:

Let’s implement the URL parameter in an Express Application and see it in action.

Step 1: Create an Express Application with the below commands.

npm init -y

Step 2: Install Express library with npm and add it to dependency list

npm install --save express

Example: Adding server.js

• In the project directory, create a file named index.js.
• Create an express server in the file and listen for connections.

Javascript

// server.js

// create an express object
const app = require("express")();

// server port
const PORT = 8080;

// listen for connections
app.listen(PORT, () => {
    console.log(`server is listening at port:${PORT}`);
});

• In the above code, an express app is created by importing the express library.
• Server is listening in the 8080 Port for any incoming request, on successful start server will print a log in the console.

Approach 1: Using queries

In this method, the URL parameter will be send in the URL as queries. Queries are appended at the end of actual url with a question character “?” appended at the last. Every query value will be mapped as key – value pairs and will be delimited with an ampersand “&” symbol.

http://example.com/api/?id=101&name=ragul

In the above example the queries are passed like below key – value pairs

Key	Value
id	101
name	ragul

Example: Using queries:

• To use URL parameters in type of queries, use the “req.query” property from request object in Express.
• Express will automatically add the queries from URL in the req.query as a Javascript Object.

Javascript

// server.js

// create an express object
const app = require("express")();

// server port
const PORT = 8080;

// using queries
app.get("/api", (req, res) => {
    // get the URL parameters passed by
    // query with req.query
    const queries = req.query;
    res.send(queries);
});

// listen for connections
app.listen(PORT, () => {
    console.log(`server is listening at port:${PORT}`);
});

• queries are being read from req.query and just simply returned as response.

Output:

using URL parameters with req.query

Approach 2: Using Route parameter

In route parameters, instead of sending as queries, embed the value inside the actual URL itself.

For example

http://example.com/api/:id/:name

Here, userid and username are placeholder for route parameter. To use the above URL parameter send the request like below.

http://example.com/api/101/ragul

• :userid is mapped to 101
• :username is mapped to ragul

Example: Using route params

• To use the route parameter, define the parameters in the URL of the request.
• Every parameter should be preceded by a colon “:”
• Access the route parameters from the request object’s params property, it will return a Javascript Object.

Javascript

// server.js

// create an express object
const app = require("express")();

// server port
const PORT = 8080;

// Using params
app.get("/api/:id/:name", (req, res) => {
    // get the URL parameter from URL
    // with req.params
    const params = req.params;
    res.send(params);
});

// listen for connections
app.listen(PORT, () => {
    console.log(`server is listening at port:${PORT}`);
});

The above code will map the id to the immediate value next to “/api/” and for the name it will add the second next value in the URL parameter.

Output:

using URL parameters with req.params