javascript function declaration VS function expression

gistfile1.txt

function f(x) {
  console.log(`x this ${this}`)
  return y(x) + 1
}
// calling this here works, y is hoisted
console.log(f.bind(123)(3))
function y(y) {
  console.log(`y args ${arguments[0]}`)
  console.log(`y this ${this}`)
  return y * 2
}

const g = (x) => {
  console.log(`g this ${this}`)
  return z(x) + 1
}

// calling this here will crash because lack of z
// console.log(g.bind(123)(3))

const z = (x) => {
  console.log(`z args ${arguments[0]}`)
  console.log(`z this ${this}`)
  return 2 * x
}
console.log(g.bind(123)(3))

// REDECLARATION

// the below is legal, doesn't throw
// function f() { console.log('REDECLARED') }

// the below won't work
// const f = (x) => x + 10000

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