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Express.js – router.param() Method
router.param(name, callback) adds a callback to the route parameters where name defines the name of the parameter and callback is the callback function.
Following are the parameters of the callback function −
req – the request object
res – the response object
next -- the next middleware
name – value of the name parameter
Syntax
router.param( name, callback )
Example
Create a file with the name "routerParam.js" and copy the following code snippet. After creating the file, use the command "node routerParam.js" to run this code as shown in the example below −
// router.param() Method Demo Example
// Importing the express module
var express = require('express');
// Importing the route module
const userRoutes = require("./router");
// Initializing the express and port number
var app = express();
var PORT = 3000;
// Defining the route
app.use("/", userRoutes);
app.listen(PORT, function(err){
if (err) console.log(err);
console.log("Server listening on PORT", PORT);
});router.js
// Importing the express module
const express = require("express");
const router = express.Router();
// Defining the router param with its value
router.param("userId", (req, res, next, id) => {
console.log("I am called first");
next();
});
router.get("/user/:userId", (req, res) => {
console.log("I am called next");
res.end();
});
// Export router as a module
module.exports = router;Hit the following Endpoint with a GET request −
http://localhost:3000/user/21
Output
C:\home
ode>> node routerParam.js Server listening on PORT 3000 I am called first I am called next
Updated on: 28-Mar-2022
921 Views
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