Middleware in Expressjs
Hello viewers, whats up!! Here i am back again with the new series of Nodejs. Node.js is an open-source, cross-platform JavaScript runtime environment that allows developers to run JavaScript code outside of a web browser. It is built on the V8 JavaScript runtime engine, which is the same engine that powers the Google Chrome browser.
Node.js is commonly used for building APIs (Application Programming Interfaces). You can create RESTful APIs or GraphQL APIs using Node.js to handle HTTP requests and serve data to client applications.
Key features of Node.js include:
# Asynchronous - Node.js is designed to be asynchronous, meaning it can
handle a large number of concurrent connections without the need for
multithreading.
# Single-threaded, Non-blocking I/O -
Node.js uses a single-threaded event loop to manage asynchronous
operations.
# npm (Node Package Manager): npm is the default
package manager for Node.js, allowing developers to easily manage and install
libraries and dependencies for their projects.
# Server-Side Development: Node.js is commonly used for server-side development, where it excels at
handling real-time, data-intensive applications, such as chat applications,
online gaming, and streaming services.
But Why we are using Expressjs Here, just because of incase if
you want to make API using nodejs directly then
its a very complex method to create API and integrate directly thats why we
are using Expressjs framework and in this framework with the help, you
can create RESTful API easily.
Why we need of middleware in Expressjs ?
In express.js, middleware functions have access to the request object ('req'), the response object ('resp'), and the next middleware function in the application's request-response cycle. They can perform various task, modify the request and response object, end the request-response cycle, and call the next middleware in the stack.
Middleware Types ?
- Application-level middleware
- Router level middleware
- Error-handling middleware
- Built-in middleware
- Third-party middleware
Route Level Middleware
Before stating route level, we have already told you about Application level middleware. CLICK HERE for more info.
Route level middle that is applied specifically to a particular route or group of routes in a web application. This allows developers to define middleware that is only executed for certain routes, providing a more fine-grained control over the application's behavior.
How to implement on a particular route ?
If you carefully discuss saw our about previous blog then we already know about request filter like we were used app.use(requestFilter);
const reqFilter = (req, resp, next) => {
console.log("reqFilter")
next();
}
const express = require("express");
const app = express();
const reqFilter = (req, resp, next) => {
if (!req.query.age) {
resp.send("Please provide your age");
} else if (req.query.age < 18) {
resp.send("You can't access this becuase of you are minor ");
// Please provide your age as a parameter like ?age=18
} else {
next();
}
};
app.use(reqFilter);
app.get("/", (req, resp) => {
resp.send("Welcome to Home Page")
});
app.get("/user", (req, resp) => {
resp.send("Welcome to user page");
});
app.listen(5000);
But now we want only apply middleware on particular page so don't use app.use(requestFilter); . Let's check it how we can implement on a particular page.
app.get("/user", reqFilter, (req, resp) => {
resp.send("Welcome to User Page")
});
Whole Code
const express = require("express");
const app = express();
const reqFilter = (req, resp, next) => {
if (!req.query.age) {
resp.send("Please provide your age");
} else if (req.query.age < 18) {
resp.send("You can't access this becuase of you are minor ");
// Please provide your age as a parameter like ?age=18
} else {
next();
}
};
app.get("/", (req, resp) => {
resp.send("Welcome to Home Page")
});
app.get("/user", reqFilter, (req, resp) => {
resp.send("Welcome to user page");
});
app.listen(5000);
Make middleware in different file
Why we need of separate file for this because of if we have too much routes in index.js or good pratice for us to make a separate file then it will be very complexity so for this you can first make a file in the same place where that you have index.js file so create a middleware.js file and code it.
module.exports = reqFilter = (req, resp, next) => {
if (!req.query.age) {
resp.send("Please provide your age");
} else if (req.query.age < 18) {
resp.send("You can't access this becuase of you are minor ");
// Please provide your age as a parameter like ?age=18
} else {
next();
}
};
Here above in the code only one line we have to added like module.exports =
const express = require("express");
const app = express();
const reqFilter = require('./middleware');
route.use(reqFilter);
app.get("/", (req, resp) => {
resp.send("Welcome to Home Page")
});
app.get("/user", reqFilter, (req, resp) => {
resp.send("Welcome to user page");
});
app.listen(5000);
Implement Route more Than one page except one Page
const express = require("express");
const app = express();
const reqFilter = require('./middleware');
const route = express.Router();
//app.use(reqFilter);
route.use(reqFilter);
app.get("/", (req, resp) => {
resp.send("Welcome to Home Page")
});
route.get("/user", (req, resp) => {
resp.send("Welcome to user page");
});
route.get("/contact", (req, resp) => {
resp.send("Welcome to contact page");
});
app.use('/', route);
app.listen(5000);
Here as you can see this only home page is shown as normal page except
user or contact page.
# Install redux and saga packages - CLICK HERE
# Make reducer wrapper - CLICK HERE
# Action in reducer - CLICK HERE
# Reducer in redux -
CLICK HERE
# Switch Stmt in redux -
CLICK HERE
# Get data in component from redux - CLICK HERE
# Remove from cart - CLICK HERE
# Add Redux Toolkit in react redux saga - CLICK HERE
# Configure MiddleWare saga - CLICK HERE
# Call API with Saga and Set Result in react redux saga - CLICK HERE
# Product list ui with API data in react redux saga - CLICK HERE
# Remove to Cart with ID react redux saga - CLICK HERE
# Add Routing and Make Cart Page - CLICK HERE
# Show Added To Cart Product with Price Calculation -
CLICK HERE
Disclaimer
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%20-%20AX5400(3).png "Make dynamic page with Embedded javascript template ejs")
%20-%20AX5400(3).png "Load Separate HTML Files in expressjs")
