node js filestream | node js tutorials

 _filename

_dirname

above are two glabal varialbe

_dirname - it prints current directoru

_filename - it printes current location 

process.cwd()

current working directory

process.chdir("") change directory

 

join path and string

path.sep = console = /

directories.join(path.sep);

how to base name from path

how to get ext from path

path.extname(filename)

path.basename(filename)

how to get absolute path

path.resolve(_dirname,'content','subfolder','test.txt')

users/smilga/desktop/tutorial/content/subfolder/test.txt

how to check file exists and 

red file write file then rename the file

fs is one module

var fs= require('fs');

var path= _dirname +"/mytext.txt";

fs.readFile(path, "utf8" function(error,data)

read the file in that path and then encrypt with utf8 then callback the function

i

how to rename the fuile

fs.rename

make new directory

read all the data in directory

fs.readdir(path, function (error,files){

remove directory

fs.rmdir

const {readFileSync,writeFileSync} = require('fs');

read the file 

const first = readfilesync('pathname','utf8');

write into file

write from another files too

writefilesync('path','hellow world : ${first}, ${second}',{flag:'a'})

flag new line

 

flag a means append

 

create server , console the data from file

it wil print the whole data its in mbs if it is a larage file

fs.craetereadstream

same size in ui but in response headers , transfer-encoding - chunked

readfile('path',(){})

call back function with arguments
readfile('path',(err,result){

    if(err)

{

    console.log(err)

return

}

console.log(result)

})

without utf8

readfile('path','utf8',(err,result){

    if(err)

{

    console.log(err)

return

}

console.log(result)

const first : result

writeFIle('path','here $(furst)',(err,resulte)=>{})

})

write file

read and write into same file

whats the difference between read file and read file sync

if async- if a function takes time - taht function execute late, whichone execute first that one wil execute

before excute of readfiile sync console works

but line by line works which one take large time that throw to last time means it runs on sepaerately

if it works over it prints immedieatly

next line not stop for before line

sync

async

readFile

with promise

now below works as sync

means when this called it must return becaue of promise  (call back)

till that next line waits

const start = async() => {}

call back in async funciton

const start = async() => {

const first = await getText('./content/first.txt');

console.log(first);

}

in try catch

one function for number of file paths

const start = async() => {

try{

const first = await getText('./content/first.txt');

const second = await getText('./content/second.txt');

console.log(first);

}catch(error)[

console.log(error)

}

}

 

calling above function - invoke

start();

instead of writing get text function seperate use

util

util is a ibuilt funciton

without util and with promises

 

in above thing, if read one file that file data write to another fileif the next funciton in next line , its not wokrs because it is async

so for that purpose in call back we write another funciion like below