Express.js | app.METHOD() Function - GeeksforGeeks

18 Jun, 2020
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 representing 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.
Path: The path for which the middleware function is invoked and can be any of:A string representing a path.A path pattern.A regular expression pattern to match paths.An array of combinations of any of the above.
A string representing 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.
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 express module:
You can visit the link to Install express module. You can install this package by using this command.npm install expressAfter installing express module, you can check your express version in command prompt using the command.npm version expressAfter 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
You can visit the link to Install express module. You can install this package by using this command.npm install express
npm install express
After installing express module, you can check your express version in command prompt using the command.npm version express
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
node index.js
Filename: index.js
var express = require('express');var app = express();var PORT = 3000;  // Handling GET Requestapp.get('/user', function(req, res){    res.send("Handled GET Request");});  // Handling POST Requestapp.post('/user', function(req, res){    res.send("Handled POST Request");});  // Handling DELETE Requestapp.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:
The project structure will look like this:Make sure you have installed express module using the following command:npm install expressRun index.js file using below command:node index.jsOutput:Server listening on Port 3000

The project structure will look like this:
Make sure you have installed express module using the following command:npm install express
npm install express
Run index.js file using below command:node index.jsOutput:Server listening on Port 3000

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.
Express.js
Node.js
Web Technologies
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