https://github.com/mthirumalai2905/node
Node.js is a runtime environment that allows you to execute JavaScript code outside of a web browser.
https://github.com/mthirumalai2905/node
expressjs mongodb nodejs
Last synced: 2 months ago
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Node.js is a runtime environment that allows you to execute JavaScript code outside of a web browser.
- Host: GitHub
- URL: https://github.com/mthirumalai2905/node
- Owner: mthirumalai2905
- Created: 2024-03-29T06:11:17.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2024-12-04T12:31:54.000Z (6 months ago)
- Last Synced: 2025-04-14T06:08:28.059Z (2 months ago)
- Topics: expressjs, mongodb, nodejs
- Language: JavaScript
- Homepage:
- Size: 874 KB
- Stars: 2
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
## Node.js
``Node.js is a javascript runtime Environment Built upon Chrome's V8 Engine``
## History of Nodejs
```txt
In 2009 an idea came in the mind of Ryan Dahl(Google Engineer)
that why not run javascript
outside browser, so he took v8 engine and embedded in a c++ program
and called it Node.exe later then came to be known as Node.js
```
```txt
In 1995 Netscape written a program called Netscape Enterprise server
for a runtime javascript but it didnt work
```
## When to Use Nodejs
1) I/O Bound
2) Data Streaming Applications
3) Real time chat Applications
## Node JS REPL
The `REPL` feature of Node is very useful in experimenting with Node.js codes and to debug javascript codes.
**R** - `Read` user's input parses the input into Javascript data-structure,and stores in memory
**E** - `Eval` Takes and evaluates the data structure
**P** - `Print` Prints the result
**L** - `Loops` the above command until the user presses ctrl-c twice
```bash
node
Welcome to Node.js v20.10.0.
Type ".help" for more information.
> 5 + 3
8
> _ + 2
10
>
```
```bash
// Create files thorugh terminal
type > index.js
//Read the inside file
type index.js
```
**In REPL press Tab twice**
```bash
AbortController
AbortSignal
AggregateError
Array
.
.
.
.
....
constructor
> setTimeout
[Function: setTimeout] {
[Symbol(nodejs.util.promisify.custom)]: [Getter]
}
> clearTimeout
[Function: clearTimeout]
> clearTimeout()
undefined
> fs
......
```
## Modules in Node JS
**File System**
```javascript
const fs = require('fs');
//creating a new file
fs.writeFileSync("read.txt", "Bench Press 100 kilos withing 3 months")
//It overides the previous data present in the file
fs.writeFileSync("read.txt", "Bench Press 100 kilos withing 3 months will this overide the previous data")
//Add datas to the existing file
fs.appendFileSync("read.txt", " \nLol am already benching 100 wbu ?")
//Reading the existing data
const buf_data = fs.readFileSync("read.txt", "utf-8");//Takes 2 arguments file name and encoding-type
console.log(buf_data)
//Rename File
fs.renameSync("read.txt", "readandwrite.txt");
//Buffer - is an additional data type available in node to store binary datas
```
## CRUD OPERATIONS USING FS MODULES
```javascript
const fs = require('fs');
try {
// Create the folder
try {
fs.mkdirSync('folder');
console.log("Folder created successfully");
} catch (err) {
if (err.code === 'EEXIST') {
console.log("Folder already exists");
} else {
throw err; // Throw error if it's not 'EEXIST'
}
}
// Create a new file
fs.writeFileSync('folder/new.txt', 'Node creating file within the folder');
console.log("File created successfully");
// Append data to the file
fs.appendFileSync('folder/new.txt', '\nappending some data');
console.log("Data appended to the file successfully");
// Read data from file
const data = fs.readFileSync('folder/new.txt', 'utf8');
console.log("Data read from file:", data);
// Copy data from one file to another
const sourceData = fs.readFileSync('folder/new.txt', 'utf8');
fs.writeFileSync('folder/blah.txt', sourceData);
console.log("Data copied to another file successfully.");
// Rename the file
fs.renameSync('folder/new.txt', 'folder/renamed.txt');
console.log("File renamed successfully.");
// Delete the file
fs.unlinkSync('folder/blah.txt');
console.log("File deleted successfully.");
// Delete the folder
fs.rmdirSync('folder');
console.log("Folder deleted successfully.");
} catch (err) {
console.error("Error occurred:", err);
}
```
## Importing and Exporting module
```javascript
// The file which will be exported
const add(a,b){
return a + b
}
const sub(a,b){
return a - b
}
module.exports = {add, sub}
```
```javascript
// The file which will be importing that module
const {add,sub} = require('./file_name');
console.log(add(5,5));
console.log(sub(10,5));
```
```javascript
//console.log(__dirname);: This will print out the absolute path of the directory where the //current JavaScript file resides.
//console.log(__filename);: This will print out the absolute path of the current JavaScript //file itself.
console.log(__filename);
console.log(__dirname);
```
## Customizing the views directory for template engines(hbs,ejs,pug)
```javascript
const templatePath = path.join(__dirname, "../templates");
app.set("views", templatePath);
```
## Partials
```javascript
// Similar to components structure used in React
{{>header}}
```