# What is Nodejs?

- Node.js is a platform built on Chrome's JavaScript runtime for easily building fast and scalable network applications. Node.js uses an event-driven, non-blocking I/O model that makes it lightweight and efficient, perfect for data-intensive real-time applications that run across distributed devices.
- Node.js is an open source, cross-platform runtime environment for developing server-side and networking applications. Node.js applications are written in JavaScript, and can be run within the Node.js runtime on OS X, Microsoft Windows, and Linux.

- Node.js also provides a rich library of various JavaScript modules which simplifies the development of web applications using Node.js to a great extent.

***Reference***: https://www.tutorialspoint.com/nodejs/nodejs_introduction.htm

# What is Expressjs?

Express is a minimal and flexible Node.js web application framework that provides a robust set of features for web and mobile applications.

With a myriad of HTTP utility methods and middleware at your disposal, creating a robust API is quick and easy.

Express provides a thin layer of fundamental web application features, without obscuring Node.js features that you know and love.

***Referecne***: https://expressjs.com/

## Frameworks built on Expressjs:

Check [Here!](https://expressjs.com/en/resources/frameworks.html)

# Practical Talk With Example:

We need to Create an attendance system APIs where user can:

1. Register himself on the system
1. Login to the system
1. Check in on a certain time
1. Check out on a certain time
1. List attended users today (check in time, check out time)

## ERD:


#### Where:
- checkin has default value true.
- checkout has default value false.
- createdAt will be filled using (sequelize)
- updatedAt will be filled using (sequelize)
- userId will be filled by us.

## User Stories:
1. User can register to the system.
2. User can login to the system.
3.
* User can check in to the system using an API where he can only check in only one time today.
* if user check in the second time then an error will be sent as a response.
5. * User check out from the system where he has check in record today.
* if there is no check in then an error message will be sent as a response.
* if the user check out today then an error message will be sent as a response.
7. Manager can get a list of attended users for this month with counting attended days for each user.

## Technically:
- [ ] 1. creating Register API.
- [ ] 2. creating middleware to filter unauthenticated users.
- [ ] 3. Creating Login API.
- [ ] 4. Creating Check In API.
- [ ] 5. Creating Check Out API.
- [ ] 6. creating Middelware to filter out non-managerial users.
- [ ] 7. Creating User attendance counter API

### Resources:
[Github Repository to check the full code](https://github.com/poode/simple-attandance-system)
[Postman Collection import it inside Postman Application](https://www.getpostman.com/collections/3cd8c2a568b6972444a1)
[Simple Regex Explanation Of One Pattern Used](https://regex101.com/r/4X8ogB/1)

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## To Learn More:
**[Learn Nodejs By Practice](https://nodeschool.io/)**
**[freecodecamp.org To learn javascript basics](https://www.freecodecamp.org/learn)**
**[expressjs Documentation](http://expressjs.com/en/4x/api.html)**