If you really want to use splice(), you can spread the string to an array, invoke splice() on the array, and join() the results back together:

const removeFromString = (s, x, y) => {
  const array = [...s];
  array.splice(x, y);
  return array.join('');
}

console.log(removeFromString('Elie', 2, 2));

I think this is what you want to do.

function removeFromString(string, start, count) {
    let str = string.split('');
    str.splice(start, count);
    return str.join('');
}

console.log(removeFromString('Elie', 2, 2));

Try this:

function removeFromString(str, start, end) {
  let arr = Array.from(str);
  arr.splice(start, end);
  return arr.join(String());
}

and then use:

removeFromString('Elie', 2, 2);