# Introduction

### Introduction

* Environment to run javascript outside browser
* Built on Chrome's V8 JS engine
* Full Stack

***

### Browser JS vs Node JS

| Browser          | Node.Js          |
| ---------------- | ---------------- |
| DOM              | No DOM           |
| Window           | No Window        |
| Interactive Apps | Server Side Apps |
| No Filesystem    | Filesystem       |
| Fragmentation    | Versions         |
| ES6 Modules      | CommonJS         |

***

### Globals

| Keyword      | Action                                             |
| ------------ | -------------------------------------------------- |
| \_\_dirname  | path to current directory                          |
| \_\_filename | file name                                          |
| require      | function to use modules (CommonJs)                 |
| module       | info about current module (file)                   |
| process      | info about env where the program is being executed |

***

### Modules

* Encapsulated Code, Only share mininum
* Exported using `module.exports`
* Imported using `require()`

#### Built-in Modules

* OS
* PATH
* FS
* HTTP

#### Nodemon

* Installed as a global package usually
* Automatically restarts the app when modifying the code
* Included in `package.json` scripts as `nodemon app.js`

***

### Global Package vs NPX

* We should avoid installing dependencies globally since they can cause issues
* We should use NPX (Node Package Runner) to run packages without having to install them locally or globally

***

### package-lock.json

* When we install a node package of certain version, it also have its own dependencies of specific version
* this file contains the versions of the additional dependencies of the installed packages

***

### Package versioning (a.b.c)

* Whenever **a** changes, it means a major change (breaking change)
* **b** change is a minor change, it is backward compatible
* **c** change is a patch or bug fix

***


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://notes.nomanaziz.me/development/backend/nodejs/introduction.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.