Shuffle function that doesn't change original array JS [duplicate]

This question already has an answer here:

• Copying array by value in JavaScript 19 answers

var nums = [1,2,3,4,5];

function shuffle(array){
  var newArr = Object.assign(array);
  var counter = newArr.length;

  while(counter > 0){
    var index = Math.floor(Math.random() * counter);
    counter--;

    temp = newArr[counter];
    newArr[counter] = newArr[index];
    newArr[index] = temp;
  }
 return newArr;

}
shuffle(nums);

The newarray comes back shuffled but so does the original array. I thought by using object.assign that it would create a copy of the array and that the original array wouldn't be touched but used as a copy. What am I doing wrong?