const dates = [
  {value: 'Jul 19'},
  {value: 'Aug 19'},
  {value: 'Sep 19'},
  {value: 'Oct 19'},
  {value: 'Nov 19'},
  {value: 'Dec 19'},
  {value: 'Jan 20'},
];

function randomDelta() {
  return Math.floor(Math.random() * Math.floor(10)) * 50;
}

function getActualSpent(budget) {
  if (isNaN(budget)) {
    return randomDelta();
  } else {
    return budget + randomDelta();
  }
}

const newCampaigns = campaigns.map(c => {
  const {actualSpent} = c;
  const budgets = dates.map(({value, realIndex}, index) => ({
    actualSpent: getActualSpent(actualSpent),
    realIndex: index + 1,
    value,
  }));
  console.log({
    ...c,
    budget: budgets
  });
  return {
    ...c,
    budget: budgets
  }
});