function list(names){
  const result = [];
  for (let item of names.slice(0, names.length - 2)) {
    result.push(names[i].name);
  }

  return `${result.join(', ')} & ${names[names.length - 1]}`
}

list([{name: 'Bart'},{name: 'Lisa'},{name: 'Maggie'},{name: 'Homer'},{name: 'Marge'}]);

//'Bart, Lisa, Maggie, Homer & Marge'