reverse.js

let arr1 = [1,2,3,4,5];
let arr2 = [1,2,3,4,5,6,7,8,9,10];
function reverse(arr)
{
  var len = arr.length;
  var middle = Math.floor(len / 2);
  
  var start = 0;
  var end = len - 1;
  
  
  while(start < middle && end > middle)
  { 
       var temp = arr[start];
       arr[start] = arr[end];
       arr[end] = temp;
    
       start += 1;
       end -= 1;
  }
  
  console.log(arr);
  
}

reverse(arr1);
reverse(arr2);