imperative-declative.js

const numbers = [1, 2, 3, 4, 5]

console.time('Imperative')

function squared(numbers) {
  let arr = []
  for ( let i = 0; i < numbers.length; i++ ) {
    arr.push( numbers[i] * numbers[i] )
  }
  return console.log(arr)
}

squared(numbers)

console.timeEnd('Imperative')

console.time('Declarative')

console.log( numbers.map( num => num * num ) )

console.timeEnd('Declarative')

/*
Imperative:22.512ms
Declarative:1.87ms
*/