TypeError Symbol(Symbol.iterator) of undefined created by devtanc - https://repl.it/@devtanc/TypeError-SymbolSymboliterator-of-undefined

TypeError Symbol(Symbol.iterator) of undefined.js

const taskData = {}

formatAppointment({ task: [], assignment: undefined })

function formatAppointment({ task, assignment }) {
  const [ taskData ] = task;
  // Error shows here due to the assignment property being a non-iterable value
  const [ assignmentData ] = assignment;

  return {
    schedule: {
      end: assignmentData.finish[0],
      start: assignmentData.start[0],
    },
    address: {
      zip: taskData.postcode[0],
      city: taskData.city[0],
      state: taskData.state[0],
      street: taskData.street[0],
      country: taskData.country[0],
    },
    customer: {
      name: taskData.name[0],
      email: taskData.email[0],
      phone: taskData.phone[0],
    },
  };
};