E0159: unexpected literal in parameter list; expected parameter name

A function parameter can be a variable name, an array destructuring, or an object destructuring. It is a syntax error for a function parameter list to contain a number literal:

function drop(array, count, 0) {
  return array.slice(count);
}

To fix this error, make the literal a default value of a parameter:

function drop(array, count = 0) {
  return array.slice(count);
}