let state = {
  stars: 5,
  list: [1,2,3,4,5],
  comment: { user: 'weber', note: 'cyberspace' }
}

//1. replace scalar variable:
var s1 = Object.assign({}, state, { stars: 8 });
console.info('1: ', JSON.stringify(state), JSON.stringify(s1));

//2. replace array:
var s2 = Object.assign({}, state, { list: state.list.slice(2) });
console.info('2: ', JSON.stringify(state), JSON.stringify(s2));

// 3. replace object:
var comment = state.comment
var s3 = Object.assign({}, state, {
  comment: {
    user: 'what-ever-user',
    note: comment.note
  }
});
console.info('3: ', JSON.stringify(state), JSON.stringify(s3));