function_definition.js

'use strict'
const square = (x = 0) => {
  return x * x
}
const sum = (x = 0, y = 0) => {
  return x + y
}
console.log(square(2))
console.log(square())
console.log(sum(10, 5))
console.log(sum(3, 7))

let name = 'John'
let lastName = 'Smith'
const makeUser = ({ name, lastName }) => {
  let user = { name, lastName }
  return user
}
console.log(makeUser({ name, lastName }))

const adding = (...numbers) => {
  let sum = 0
  for (let number of numbers) {
    sum += number
  }
  return sum
}

console.log(adding(1,2,3,4,5))
console.log(adding(14,16,9))