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Web Technology

What is Middleware in Express.js ?

How to skip a middleware in Express.js ?

Last Updated : 09 Apr, 2021

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If we want to skip a middleware we can pass parameters to the middleware function and decide based on that parameter which middleware to call and which middleware to not call.

Prerequisite:

express.js: To handle routing.

Setting up environment and execution:

Step 1: Initialize node project
```
npm init
```
Step 2: Install required modules
```
npm install express
```

Example:

index.js

const express = require("express"); // const database = require('./sqlConnection');  const app = express();  // Start server on port 5000 app.listen(5000, () => {   console.log(`Server is up and running on 5000 ...`); });  // define middleware 1 let middleware1 = (req, res, next) => {      // decide a parameter     req.shouldRunMiddleware2 = false;      console.log("Middleware 1 is running !");     next(); }  // define middleware 2 let middleware2 = (req, res, next) => {     if(!req.shouldRunMiddleware2) {         console.log("Skipped middleware 2");         return next();     }      console.log("Middleware 2 is running !"); }  // define middleware 3 let middleware3 = (req, res, next) => {     console.log("Middleware 3 is running !"); }  // create route for home page '/' app.get("/", middleware1, middleware2, middleware3);

Output: Run the below command to start the server. After that go to http://localhost:5000 on browser to see output in console

node index.js

In browser.
Console:

What is Middleware in Express.js ?

P

pratikraut0000

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Article Tags :

Web Technologies
Node.js
Express.js

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