- Whenever you will connect your application to a database, always wrap the connection code inside a try catch block and promises/async await. Dont assume that the connection will always work.
- Database is an another continent.
Custom API Responses and Error Handling
Q. When do we use app.use() in express and nodejs application
app.use() is a method used to mount middleware functions at a specified path.
app.use() methods are used for configurations and middleswares(with or without url paths)
the files inside utils/ are there for wrapping frequent async/await and try...catch blocks in controllers and functions.
Using cloudinary to store the avatar and coverImage
Difference between bcrypt and bcryptjs
learn about cors
In mongose models, we can define middleware(also pre-hooks) before the saving the data in the DB JWT is a bearer token- joh bhi mujhe ye bhejega, mai usko data bhejunga
here, Hitesh is using both cookeis and sessions, quite secure. Access token is not stored in the Database, but Refresh token is
File Upload is handled by backend Engg For File Uploads, various services. and writing the function in a separate utiliity file
Slangish way to remember middlewares- jaane se pehle mujhse milkar jaana Multer is commonly used package for file uploading Express-fileupload is an older way Initially, file uploaded using multer
multer to local server to cloudinary In production-grade settings, file is taken from the user and stored in the local server temporarily, then using cloudinary, file from local storage and sent to the cloud server. Done incase of any upload issues, the process can re-attempted
Why multer code is used a middleware? jaha jaha file uploading capabilities ki jarurat hogi waha waha ye middleware inject kar denge
Need to read about multer, especially its other options and config
Backend Engineers first consider all the corner cases, scenarios and design decisions, and not just write routes and controllers half-ass way. that is what they are paid for.
URL/URI/URN
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HTTP Headers metadata --> key-value sent along with req and res Headers are used for caching, authentication, manage State(example-logged in, guest login) Before 2012, headers used to start with X-prefix, now deprecated.
Request Headers -> From Client Response Headers -> From Server Representaion Headers -> encoding/compression Payload Headers -> data
Most Common Headers Accept: application/json User-agent Authorization(Bearer ) Content-Type Cookie Cache-control- CORS Access-Control-Allow-Origin Access-Control-Allow-Credentials Access-Control-Allow-Method
Security Cross-Origin-Embedder-Policy Cross-Origin-Opener-Policy Content-Security-Policy X-XSS-Protection
These are just headers, just info, nothing happens on its own. we have to define the header's behaviour
HTTP Methods GET : Retrieve a resource HEAD : No message body( Response headers only) OPTIONS : what operations are available TRACE : loopback test ( get some data) DELETE : remove a resource PUT : replace a resource POST : interact with resource(mostly add) PATCH : change a part of resource
We are supposed to write the logic of the methods on our own, nothing happends automatically.
HTTP Status Code
- 1xx Informational
- 2xx Success
- 3xx Redirection
- 4xx Client Error
- 5xx Server Error
| Status | Codes |
|---|---|
| 100 Continue | 400 Bad Request |
| 102 Processing | 401 Unauthorized |
| 200 OK | 402 Payment Required |
| 201 Created | 404 Not Found |
| 202 Accepted | 500 Internal Server Error |
| 307 Temporary Redirect | 504 Gateway time out |
| 308 Permanent Redirect |
Channels and Subscribers
if you want to count the number of subscribers of a channel Chai aur Code, we will select all the documents containing the channel Chai aur Code.
How many channels the subscriber Vishal has subscribed to? -> Select the documents containing subscriber as Vishal and pick out the channels list.