Callback in javascript

const fs = require('fs')
fs.readFile('/etc/passwd', (err, data) => {
  if (err) {
    console.error(err)
    return
  }
  console.log(data.toString())
})

Sử dụng callback rất hạn chế ví dụ :

fs.readFile(fileA, function (err, data) {
  fs.readFile(fileB, function (err, data) {
    // ...
  })
}

Extend Object javascript

Detect when your site is visible to users

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.

try/catch es10

An update for developer convience allows the use of try/catch without an explicit e Error reference in the catch call.

Object.keys và Object.getOwnPropertyNames