js splice not mutation code example

Example 1: javascript splice without changing array

var myArray = ["one", "two", "three"];
var cloneArray = myArray.slice();

myArray.splice(1, 1);

console.log(myArray);
console.log(cloneArray);

Example 2: how to replace array element in javascript without mutation

function replaceAt(array, index, value) {
  const ret = array.slice(0);
  ret[index] = value;
  return ret;
}
const newArray = replaceAt(items, index, "J");