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https://github.com/lucky-kashyap/backend
Start with Backend
https://github.com/lucky-kashyap/backend
Last synced: 7 days ago
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Start with Backend
- Host: GitHub
- URL: https://github.com/lucky-kashyap/backend
- Owner: Lucky-Kashyap
- Created: 2023-08-24T09:20:30.000Z (about 1 year ago)
- Default Branch: main
- Last Pushed: 2024-09-16T17:35:27.000Z (about 2 months ago)
- Last Synced: 2024-09-16T21:45:01.080Z (about 2 months ago)
- Language: JavaScript
- Size: 56.6 KB
- Stars: 0
- Watchers: 1
- Forks: 0
- Open Issues: 0
-
Metadata Files:
- Readme: README.md
Awesome Lists containing this project
README
# Node JS Learning
## File System Module
- write file
const fs = require("fs");
fs.writeFile('abcd.txt','hey hello',(err)=>{
if(err) console.log(err);
else console.log('file created');
})
- Read file
fs.readFile("abcd2.txt", "utf8", function (err, data) {
if (err) console.log(err);
else console.log(data);
});
- Update file
fs.appendFile("abcd.txt", " Lucky Kashyap", (err) => {
if (err) console.log(err);
else console.log("append file");
});
- Rename file
fs.rename("abcd.txt", "test.txt", (err) => {
if (err) console.log(err);
else console.log("rename file");
});
- Delete file
fs.unlink("test.txt", (err) => {
if (err) console.log(err);
else console.log("delete file");
});
- creating folders in Node JS
fs.mkdir("lolo", (err) => {
if (err) console.log(err);
else console.log("make directory");
});
- Reading folders
fs.readdir("lolo", (err, files) => {
if (err) console.log(err);
else console.log(files);
});
// 1 for file
// 2 for folder
- Deleting folders
fs.rmdir("lolo", (err) => {
if (err) console.log(err);
else console.log("deleted");
});
fs.rm("lolo", { recursive: true }, (err) => {
if (err) console.log(err);
else console.log("deleted");
});
- synchronous APIs (Blocking vs. Non-blocking)
fs.readFileSync("abcd.txt", "utf8");
## HTTP Module
const http = require("http");
var server = http.createServer(function (req, res) {
res.end("server runs successfully");
});
server.listen(3000);
- Routing
var server = http.createServer(function (req, res) {
// console.log(req.url === "/");
// res.end("server runs successfully");
if (req.url === "/") {
res.end("hey");
} else if (req.url === "/profile") {
res.end("profile page");
} else {
res.end("page not found");
}
});
## HTTP Methods
- GET
- POST
- PATCH
- DELETE
- PUT
## STATUS CODE
- 1xx Informational Responses: These codes indicate that the server has received the request and the process is continuing.
- 100 Continue: The server has received the request headers, and the client should proceed to send the request body.
- 101 Switching Protocols: The requester has asked the server to switch protocols, and the server has agreed to do so.
- 2xx Successful Responses: These codes indicate that the request was successfully received, understood, and accepted.
- 200 OK: The request has succeeded.
- 201 Created: The request has been fulfilled and a new resource has been created.
- 202 Accepted: The request has been accepted for processing, but the processing has not been completed.
- 3xx Redirection Messages: These codes indicate that further action needs to be taken by the user agent to fulfill the request.
- 301 Moved Permanently: The resource requested has been permanently moved to a new URL.
- 302 Found: The resource is temporarily located at a different URL.
- 304 Not Modified: The resource has not been modified since the version specified by the request headers.
- 4xx Client Error Responses: These codes indicate that the client seems to have made an error.
- 400 Bad Request: The server could not understand the request due to invalid syntax.
- 401 Unauthorized: The client must authenticate itself to get the requested response.
- 403 Forbidden: The client does not have access rights to the content.
- 404 Not Found: The server can not find the requested resource.
- 5xx Server Error Responses: These codes indicate that the server failed to fulfill a valid request.
- 500 Internal Server Error: The server has encountered a situation it doesn't know how to handle.
- 502 Bad Gateway: The server, while acting as a gateway or proxy, received an invalid response from the upstream server.
- 503 Service Unavailable: The server is not ready to handle the request, often due to maintenance or overload.
## EXPRESS JS
- Set up express
const express = require("express");
const app = express();
let port = 3000;
app.get("/", (req, res) => {
res.send("Hello World!!");
});
app.listen(port, () => {
console.log("start server");
});
- Handling non-existent routes
app.get("*", (req, res) => {
res.send("Hello World!!");
});
- More on Express
- app : constant
- get : method
- route : '/' path
- handler : middleware function
#### Middlewares
- The function which have three parameters request, response, next called middleware
app.use((req, res, next) => {
console.log("Another middleware..!!!");
next();
});
#### Express Session
app.use(
expressSession({
secret: "random stuff",
resave: false,
saveUninitialized: false,
})
);
app.get("/create", (req, res, next) => {
req.session.polo = true;
res.send("Done..!!!");
});
#### Connect flash middleware:
- ek route mein data save krke dusre route mein bhejna
- Ex: login (Error in credentials)
- Using this we need to configure express session
const flash = require("connect-flash");
app.use(flash());
app.get("/", (req, res) => {
req.flash("error", "Invalid credentials");
res.redirect("/error");
});
app.get("/error", (req, res) => {
let msg = req.flash("error");
res.send(msg);
});
#### CORS
- Use cors package
npm i cors
app.use(cors());
#### Cookie Parser:
- use cookie
res.cookie("banned", "true");
console.log(req.cookies.banned);
#### Use morgan:
- For more info (HTTP request logger middleware for node.js)
const morgan = require("morgan");
app.use(morgan("tiny"));
app.use(morgan("short"));
app.use(morgan("combined"));
#### Request & Response
- frontEnd > BackEnd > FrontEnd
- req : data come from browser
- res : send via server
app.get("/", (req, res) => {
// console.log(req);
// console.log(req.params);
// console.log(req.body);
// console.log(req.cookies);
// console.log(req.query);
// console.log(req.ip);
// console.log(req.headers);
// console.log(req.url);
console.log(req.method);
res.send("Hey");
});
#### Dynamic Routing
- Static
app.get('/username/harsh',(req,res)=>{
res.send('username harsh');
});
- Dynamic
app.get("/profile/:name", (req, res) => {
// console.log(req.params.name + 's page');
let { name } = req.params;
console.log(name);
res.send("profile page " + name);
});
app.get("/author/:username/:age", (req, res) => {
let { username, age } = req.params;
res.send("something about " + username + " who is of " + age);
});
##### Server side Rendering
- Use EJS template engine
npm i ejs
app.set('view engine','ejs')
- create a views folder
- create a view index.ejs
- load the html in the ejs page
- and use res.render in place of the res.send to render any page from views folder
- Handle Form
- Make form in index.ejs
- make sure we have name attribute in all inputs nd check its method
- we set action='/check'
- And set check route in index.js file
app.get('/check',(req,res)=>{
console.log(req.query);
res.send('form handle');
})
- And for post method & make sure to include these two methods in POST method
app.use(express.json());
app.use(express.urlencoded({ extended: true }));
app.post('/check',(req,res)=>{
console.log(req.body);
res.send('form handle');
})
#### HTTP Methods in API Development
- GET
- POST
- PUT
- PATCH
- DELETE
#### Error Handling
- Two types error
- top level error
- Reference Error (Req/Res) cycle
app.get("/", (req, res, next) => {
try {
res.send(hey);
} catch (err) {
next(err);
}
});
app.use((err, req, res, next) => {
res.status(500).send(err.message);
// res.status(500).send("Internal Server Error");
});
- In Express.js middleware, errors are typically handled by calling the next function with an error parameter. This passes the error to the next error-handling middleware function or to the default error handler, allowing for centralized error handling in the application.
#### Understanding Postman
- A Postman collection is a group of requests and scripts organized together. It allows users to group related API requests, organize them into folders, and include scripts and variables to automate testing and documentation processes.
- Add data
let data = [1, 2, 3, 4];
app.get("/data", (req, res, next) => {
res.send(data);
});
app.post("/data/:num", (req, res, next) => {
// console.log(typeof req.params.num);
data.push(parseInt(req.params.num));
res.send(data);
});
#### Khatabook (File based Project)
- create file
- delete/ update / read / Edit
- file page
### File Module revisit
- Read file
- write file
- Rename file name
### Open any app Using Node JS
- require package
const { exec } = require("child_process");
- On windows
exec("start chrome");
exec("start msedge");
exec("start firefox");