CODEWITHSUNDEEP
javascriptnode.jsexpress
user12102894
user12102894

Reputation:

Is there any purpose of splitting up express and app?

I see these two lines in ( every ?) Express app.

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

I have to wonder if any parameters can be passed to express()?

Checked here and did not see any

https://expressjs.com/en/4x/api.html

Why are some methods on express() and some on app()?

It seems like they should be combined and have all methods on one object.

Upvotes: 1

Views: 61

Answers (2)

jfriend00
jfriend00

Reputation: 707148

Is there anything I can do only with express?

The reason for doing two separate lines like this:

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

instead of this:

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

is that the express module has other methods on it that are sometimes needed such as:

express.static(...)               // middleware for serving static files
express.json(...)                 // middleware for parsing json requests
express.urlencoded(...)           // middleware for parsing urlencoded requests
express.Router(...)               // constructor for a new Router object

Upvotes: 0

T.J. Crowder
T.J. Crowder

Reputation: 1073968

express does not take any parameters, no. The purpose of calling it is to create the app object, so the fact you have to call it does make sense, even without parameters.

Another way you often see that written is:

const app = require("express")();

It'll need to be separate again when using ESM, though.

import express from "express"; // Or similar

const app = express();

In a comment you've said:

For example, is there anything useful I can do with out creating app? Is there anything I can do only with express?

As far as I know, you have to have create at least one Application object to do anything useful with Express. Note that you don't have to create just one app. That's the typical use case, but there's no reason you can't create multiple apps running on different ports.

You may be wondering why express can't just give you an Application object directly from require. The reason is that modules are only loaded once and cached, so what you get from require is shared. So Express exports the express function, which you use to create the Application object (or objects, plural, if you want more than one).

Upvotes: 2

Related Questions