Rewrite Array Based On Child Array Javascript

I have array of array like { 'campaigns': [{ 'name': '1st Campaign', 'books': [{ 'title': '1st book', 'primary_isbn': 'isbn1' },

Solution 1:

You could use flatMap and map like this:

const input = {campaigns:[{name:"1st Campaign",books:[{title:"1st book",primary_isbn:"isbn1"},{title:"2nd book",primary_isbn:"isbn2"},{title:"3rd book",primary_isbn:"isbn3"}]},{name:"2nd cam",books:[{title:"4th book",primary_isbn:"isbn4"},{title:"5th book",primary_isbn:"isbn5"}]}]};

const campaigns = 
  input.campaigns.flatMap(({ name, books }) => books.map(b => ({ ...b, name })))

console.log({ campaigns })