Express.js | app.METHOD() Function

The app.METHOD() function is used to route an HTTP request, where METHOD is the HTTP method of the request, such as GET, PUT, POST, and so on, in lowercase. Thus, the actual methods are app.get(), app.post(), app.put(), and so on. 

Syntax:

app.METHOD(path, callback [, callback ...])

Parameters:

• Path: The path for which the middleware function is invoked and can be any of:
  • A string represents a path.
  • A path pattern.
  • A regular expression pattern to match paths.
  • An array of combinations of any of the above.
• Callback: Callback functions can be:
  • A middleware function.
  • A series of middleware functions (separated by commas).
  • An array of middleware functions.
  • A combination of all of the above.

Installation of the express module:

You can visit the link to Install the express module. You can install this package by using this command.

npm install express

After installing the express module, you can check your express version in the command prompt using the command.

npm version express

After that, you can create a folder and add a file, for example, index.js. To run this file you need to run the following command.

node index.js

Project structure:

Filename: index.js 

const express = require('express');
const app = express();
const PORT = 3000;

// Handling GET Request 
app.get('/user', function (req, res) {
    res.send("Handled GET Request");
});

// Handling POST Request 
app.post('/user', function (req, res) {
    res.send("Handled POST Request");
});

// Handling DELETE Request 
app.delete('/remove', function (req, res) {
    res.send("Handled DELETE Request");
});

app.listen(PORT, function (err) {
    if (err) console.log("Error in server setup");
    console.log("Server listening on Port", PORT);
}); 

Steps to run the program:

Make sure you have installed the express module using the following command:

npm install express

Run the index.js file using the below command:

node index.js

Output:

Server listening on Port 3000

So this is how you can use the express app.METHOD() function which is the HTTP method of the request, such as GET, PUT, POST, and so on, in lowercase.