Answers for "launch duplicate elements within the array javascript"

duplicate an array in javascript n times

const makeRepeated = (arr, repeats) =>
  Array.from({ length: repeats }, () => arr).flat();
  
console.log(makeRepeated([1, 2, 3], 2));

function that duplicates data in array js

function doubleValues(array) {
  var newArray = [];
  array.forEach(function (el) { newArray.push(el, el); });    
  return newArray;
}

console.log(doubleValues([1,2,3]));