var express = require('express'); var app = express(), What is express()?? is it a method or a constructor? Where does it come from

Question

var express = require(\'express\'); 
var app = express();

This is how we create an express application. But what is this \'express()\'? Is it a met

Answer 1

Whenever you import a module like

const express = require('express')

express is a module with functions or objects or variables assigned to it . take a look at /lib/express

you are able to access the function createApplication inside express module as express() because the function is assigned directly to the module like

exports = module.exports = createApplication;

function createApplication(){
    var app = function(req, res, next) {
    app.handle(req, res, next);
  };
//other codes
}

so you are able to access the function createApplication just calling express() as function

now when you check out the other section of the express library, you can see a bunch of other objects attached to the exports special object as well.

/**
 * Expose the prototypes.
 */

exports.application = proto;
exports.request = req;
exports.response = res;

/**
 * Expose constructors.
 */

exports.Route = Route;
exports.Router = Router;

 // other exports

these objects or function assigned to export special object can be accessed from the import section using express as an object.

express.{name}

express.Route
express.Router etc

In the end you are just exporting a bunch of methods or objects that are attached to the module.export special object inside express js file

to read more on module.export special object go here