Javascript passing arrays to functions by value, leaving original array unaltered

Question

I\'ve read many answers here relating to \'by value\' and \'by reference\' passing for sending arrays to javascript functions. I am however having a problem sending an array

Answer 1

With ES6, you can use the spread syntax and destructuring to perform a shallow copy directly in the argument list, allowing you to keep the original array unaltered.

See example below:

const arr = [1, 2, 3, 4, 5];

function timesTen([...arr]) { // [...arr] shallow copy the array
  for(let i = 0; i < arr.length; i++) {
    arr[i] *= 10; // this would usually change the reference
  }
  return arr;
}

console.log(timesTen(arr));
console.log(arr); // unaltered