Array not reassigning after change

I have an array that contains elements my goal is to slice some of the elements inside the array, then later I want to reassign the original array with a new array which is a sublist of the original array but it seems like I can’t make that happen please help.

let arr = [1,2,3,4,5]

function subList(arr){
    for(let i = 0; i < arr.length; i++){
       let res = arr.slice(0,i)
       if(i === 3){
           arr = res;
        }
    }
      
   }
   subList(arr)

   console.log(arr)
   // expected output [1,2,3]

>Solution :

Pass in an index to the function and just return arr.slice(0, i);.

let arr = [1, 2, 3, 4, 5]

function subList(arr, i) {
  return arr.slice(0, i);
}

console.log(subList(arr, 3));