Combine

combinations.js

const categorizeValues = ([category, values]) => 
  values.map(value => Object.fromEntries([[category, value]]))

const combineCategories = (prev, curr) => 
  curr.flatMap(currEl => prev.map(prevEl => ({...prevEl, ...currEl})))

const combinations = input => 
  Object.entries(input).map(categorizeValues).reduce(combineCategories);

/*
input 
{ code: ["2xx", "3xx"], source: ["cdn", "internal"] }

output
[
  { code: '2xx', source: 'cdn' },
  { code: '3xx', source: 'cdn' },
  { code: '2xx', source: 'internal' },
  { code: '3xx', source: 'internal' }
]

input
{ code: ["2xx", "3xx"], source: ["cdn", "internal"], colors: ["blue", "red"] }

output
[
  { code: '2xx', source: 'cdn', colors: 'blue' },
  { code: '3xx', source: 'cdn', colors: 'blue' },
  { code: '2xx', source: 'internal', colors: 'blue' },
  { code: '3xx', source: 'internal', colors: 'blue' },
  { code: '2xx', source: 'cdn', colors: 'red' },
  { code: '3xx', source: 'cdn', colors: 'red' },
  { code: '2xx', source: 'internal', colors: 'red' },
  { code: '3xx', source: 'internal', colors: 'red' }
]
*/