Why can I use arrow javascript function before its initialization

I checked out Why can I use a function before it's defined in JavaScript?. and It says I can use functions before or after initialization when using Declaration Functions. However for the case of Expression Functions I need to initialize before use.

But check my code please. I used Expression Functions and I can use it even before initialization.

const x = () => {
  console.log('hello x')
  y() // why can I use it here???
}

const y = () => {
  console.log('hello y')
}

// later use somewhere in HTML
x()

>Solution :

Because it is just a definition.

If you write x() before the definition of y, there would be an error.

const x = () => {
  console.log('hello x')
  y() // why can I use it here???
}

x() // error

const y = () => {
  console.log('hello y')
}