promise in javascript

const fs = require('fs')

const readFileWithPromise = file => {
  return new Promise((resolve, reject) => {
    fs.readFile(file, (err, data) => {
      if (err) {
        reject(err)
      } else {
        resolve(data)
      }
    })
  })
}

readFileWithPromise('/etc/passwd')
  .then(data => {
    console.log(data.toString())
    return readFileWithPromise('/etc/profile')
  })
  .then(data => {
    console.log(data.toString())
  })
  .catch(err => {
    console.log(err)
  })

Có thể bạn đã miss một số snippets code

encode/decode base64 with JS

Encoding to base64 is done with the btoa command

using javascript callback style error handling

Object.keys và Object.getOwnPropertyNames

Hàm lày ngày trong tuần javascript

Rest Operator for Objects

Now we can use rest on the properties of an Object. It allows us to explicitly extract certain named variables, and assign any uncalled variables into a catchall Object.