Node JS Notes

Global objects in Node

Global Objects in Node is similar to the Global Window Object in the browser.

Broswer: Window -> returns all accessible methos within the object
node: Gloable return all the accessible methods

NB:-

Accessing Files

__dirname -> returns the absolute path of file
__filname - > return the absolute path of file with the ile name

Modules import and Export Modularity in node js

exporting file name: resources.js
importing files name: app.js

const values = [23,"hey","johne", true]
const values2 = [...values]

// export multiple rescources
modules.export = {values, values2}

const {values, values2} = require("./resources.js") //import destructuring

FileSstems Operations in Node

    const fs = require('fs')
    
    // reading file
    fs.readFile(<dir>, (err, data) => { //async fxn
        if(err){log(err)}
        log(data.toString)
    })

    // writing files
    fs.writeFile(<dirToWriteTo>, data, (err) =>{
        ...code
    })

    // making Directories
    check if dir exists

    if(!fs.existsSync(<Dir>)){
        fs.mkdir(<dir name>, (err)=>{ // rmdir removes a directories
            ... log message
        })
    }

    // deletings files

    if(fs.existsSync(<path to file>)){
        fs.unlink("path to file", (err)=>{
            .. log err if found
        })
    }

Streams and Buffers for large files

• Streams

• Buffers

• Read Streams

• Write Streams

Using Streams data can be used while it's loading

    const readStream = fs.createReadStream(<path>, {encoding: "utf8})

    const writeStream = fs.createWriteStream(<path>, {encoding: "utf8})

readStream.on('data', (chunck)=>{
    writeStream.write('\n Chunk \n')
})

// piping
reading data from read stream into the  write stream
// much easier
readStream.pipe(writeStream)

setHeader - > redirect to a particular screen.

Express MiddleWares

it's simply functions or peac of code that run between the request coming in and the response going out of the server.

Uses of Middleware can be used in:

• As a logger for looing details of every request
• Authentication check middleware for protected Routes
• Middleware to parse json data from request
• Return 404 pages

for example: 
the use((res, req)) // we use for displaying th e 404 pages.
// the use fxn runs for every request sent the Browser