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https://github.com/sundramsharma1/backend-nodejs-express

Backend With Node.js ( Express.js )
https://github.com/sundramsharma1/backend-nodejs-express

backend expressjs mern-stack nodejs

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Backend With Node.js ( Express.js )

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Backend (Node.js, Express.js)


In this repo, we will learn about backend development using Node.js with Express.js in depth.



## Prerequisites

Before you begin, ensure you have met the following requirements:
* [Node.js](https://nodejs.org/en) must be installed on your operating system.

### Run Locally

To run your program on your local machine, type this command in your command prompt and hit enter:

```bash
node .js
```

Start



# Chapter_1(Basics)
* Process = Process command is use to get details about node which is install on your local machine

```bash
node <-|
process <-|
```
* Process.argv = Process.argv is use to take command line argument to run our programm

```bash
let n = process.argv;
for(let i = 2; i < n.length; i++){
console.log("Hiii", n[i]);
};
```
* To run this program type this command on command prompt

```bash
node .js
```

lets suppose i type this

```bash
node process.js sundram mohit
```

it will produce the output as

```bash
Hii sundram
Hii mohit
```

# Chapter_2 (Exporting File or Folder)
* Require() = A built-in-function to include modules that exist in seperate files
* Modules.export = A special object


### Exporting a Single File =>
## Example =>



File.js

```bash
module.exports = 123;
```
script.js

```bash
const data = require('./File');
console.log(data);
```
O/P = 123

### Exporting a Entire Directories =>
## Example =>

* Folder Structure

```bash
main/

├── Fruits/
│ ├── Apple.js
│ ├── Banana.js
│ ├── Orange.js
│ └── index.js

└── script.js
```
* Apple.js
```bash
const apple = {
name: 'Apple',
color: 'Red',
price: 90
};

module.exports = Apple;
```

* Banana.js
```bash
const Banana = {
name: 'Banana',
color: 'Yellow',
price: 50
};

module.exports = Banana;
```
* Orange.js
```bash
const Orange = {
name: 'Orange',
color: 'Yellow',
price: 60
};

module.exports = Orange;
```
* index.js
```bash
const apple = require('./Apple');
const banana = require('./Banana');
const orange = require('./Orange');

module.exports = {apple, banana, orange};
```
* Script.js
```bash
const info = require('./Fruits');
console.log(info);
```
* O/P =

{

apple: { name: 'Apple', color: 'Red', price: 90 },

banana: { name: 'Banana', color: 'Yellow', price: 50 },

orange: { name: 'Orange', color: 'Yellow', price: 60 }

}
## Require() Vs Import
### Require() =
* We Can't Selectively load only the pices we need
* It is a old method to load any file before (ES6)
* It is used to load whole file at a time
* module.exports = file_name;
* In this method Loading is Synchronous Means line wise module loaded
### Import() =
* We can selectively load only the pices we need, which can save the memory
* It is a new method after (ES6) version and it is use to load a single module which is faster than require
* export
* In this method loading can be Asynchronous means we can be use first function or last function or any function

Express.js

## Library Vs Framework
### Library =

* A library is a collection of pre written code that can be used to perform specific tasks
* Ex - Axios

### Framework =

* A Framework is a set of pre-written code that provides a structure for developing software applications
* Ex - express.js