What is right to use Spread operator or Object.assign in Redux?

I had a little bit of confusion whether to use Spread operator or Object.assign in reducer function to apply changes to the target object.

const toggleTodo = (todo) => {
  return Object.assign({}, todo, {
    completed: !todo.completed
   });
 };

Then above mention code is using Object.assign method, and the below one is using spread operator

const toggleTodo = (todo) => {
return {
  ...todo,
  completed: !todo.completed
  };
};

Which is the appropriate method in both of these