legal-const.js

const foo = (a) => {
  // x will stay 1 forevar
  const x = 1
  
  if (a === 1) {
    // this declaration of y is scoped only to this block
    const y = 3
    
    // both x and y are defined here, as you'd expect
    console.log('x', x) // x 1
    console.log('y', y) // y 3
  } else {
    // this is a different declaration of y from above and is totes legit
    const y = 4
    
    // both x and y are defined here, as you'd expect
    console.log('x', x) // x 1
    console.log('y', y) // y 4
  }
  
  // y is not defined here
  console.log('x', x) // x 1
}