// code to create arrays with super powers !

const superArray = (initArray) => {
  const toPos = (index, target) => {
    const _index = Number(index);
    return index < 0 ? target.length + _index : _index;
  };

  return new Proxy(initArray, {
    get(target, prop) {
      const rangeSplit = prop.split(":");
      if (rangeSplit.length > 1) {
        let [from, to] = rangeSplit;
        from = toPos(from, target);
        to = toPos(to, target);
        return target.filter((a, i) => i <= to && i >= from);
      } else return Reflect.get(target, toPos(prop, target));
    }
  });
};

// usage example : 

// create a super array
const arr = superArray([10, 20, 30, 40, 50, 60, 70]);

// use it like a normal array, but with extra features!

console.log(arr[-1]); // 70
console.log(arr["1:3"]); // [20, 30, 40]
console.log(arr["3:-1"]); // [40, 50, 60, 70]