What is the function of router(app) do in the following code?

Question

Here are few lines of code.I did not understand their function.I have commented in the code the lines that I have not understood.

 var express = require('express');
 var app = express();
 var router = require('./app/router'); //not understood
 router(app); //not understood

It will be helpful I anyone can explain their function.

They probably have a `router.js` file in an `api` folder in the project. They're requiring it and using the function. — Andrew Li, May 12 '17 at 03:26
ok understood this..but In `router(app)` here app means the folder that is present named as `app ` where router file is present? — Aditya, May 12 '17 at 03:30
@AdityaJain "*here app means the folder*" `api` would be the folder (`api` != `app`). In `router(app)`, `app` refers to an object – an instance of an [Application](https://expressjs.com/en/4x/api.html#app) created by the call to `express()`. — Jonathan Lonowski, May 12 '17 at 05:19
@JonathanLonowski sorry for typo here in the question now it is `router(app)`.. — Aditya, May 12 '17 at 05:52

score 0 · Answer 1 · edited May 23 '17 at 11:54

0

var router = require('./api/router'); //not understood

There is plenty of resources out there explaining this. See e.g. What is this Javascript "require"?

router(app); //not understood

router is a function returned by require('./api/router'). The function takes one parameter app.

What the router function does ? We can't know that as it is a proprietary code located in you filesystem in a ./api/router file.

edited May 23 '17 at 11:54

Community

answered May 12 '17 at 03:40

user272735

In `router(app)` here app means the folder that is present named as `app` where router file is present? Am I correct? – Aditya May 12 '17 at 03:43
@AdityaJain No. Your questions indicate that you needs to study more JavaScript basics. Please use your preferred JavaScript resources. `require` is not part of the JavaScript but my answer provides a good link to one resource to get you started. – user272735 May 12 '17 at 03:47

score 0 · Answer 2 · answered May 12 '17 at 07:27

require function is the easiest way to include modules that exist in separate files.

usage file:

var router = require('./app/router'); 
    router(app);

router function take app as a parameter for their use.

support (/app/router.js) file:

export default function(app) {
    // code stuff 
}

2 Answers2