vrandom/lib/shuffle.js

an easy way to work with random numbers in javascript

/**
 * Makes a shallow copy of `array` to prevent the argument from being mutated.
 * @template {unknown} T
 * @param {T[]} array
 */
const shuffle = ([...array]) => {
  let currentIndex = array.length
  let temporaryValue
  let randomIndex

  // While there remain elements to shuffle...
  while (currentIndex !== 0) {
    // Pick a remaining element...
    randomIndex = Math.floor(Math.random() * currentIndex)
    currentIndex -= 1

    // And swap it with the current element.
    temporaryValue = array[currentIndex]
    array[currentIndex] = array[randomIndex]
    array[randomIndex] = temporaryValue
  }

  return array
}

module.exports = shuffle