file system and streams

file-system.js

const fs = require('fs').promises
const path = require('path')

const getData = async (dirName) => {
  try {
    const buffer = await fs.readFile(dirName)
    const data = await JSON.parse(buffer)
    return data
  } catch (err) {
    console.error(err)
  }
}

const writeDataToFile = async (dirName) => {
  try {
    const data = await getData('data.json')
    const outputDir = path.join(__dirname, 'output')

    await fs.mkdir(outputDir)

    await fs.writeFile(
      path.resolve(outputDir, 'output.txt'),
      `name of product: ${data.name}\nprice: $${data.details.price}\n`,
      { flag: 'a' }
    )

    console.log('program finished! check the output directory')
  } catch (err) {
    console.error(err)
  }
}

const main = async () => {
  const dir = path.resolve(__dirname, 'output')
  writeDataToFile(dir)
}

main()

streams.js

/*
  a dummy program to demonstrate
  my knowledge of streams in
  node.js
*/

const fs = require('fs')
const path = require('path')

// READABLE STREAMS
let data = ''
const readable = fs.createReadStream(path.resolve(__dirname, 'dummy.txt'), {
  encoding: 'utf-8',
})

readable.on('data', (chunk) => {
  return (data += chunk)
})

readable.on('error', (err) => {
  console.error(err.stack)
})

readable.on('end', () => {
  console.log('data from "flowing" readstream:', data)
})

// WRITEABLE STREAMS
const readable2 = fs.createReadStream(path.resolve(__dirname, 'dummy2.txt'))
const writeable = fs.createWriteStream(path.resolve(__dirname, 'dummy3.txt'))

readable2.addListener('data', (chunk) => {
  writeable.write(chunk)
})

readable2.addListener('end', () => {
  console.log('data from dummy2.txt is now in dummy3.txt')
})