A MirageJS serializer to convert all IDs to integers

serializeIds.js

// convert single string id to integer
const idToInt = id => Number(id)

// convert array of ids to integers
const idsToInt = ids => ids.map(id => idToInt(id))

// check if the data being passed is a collection or model
const isCollection = data => Array.isArray(data)

// check if data should be traversed
// should match the structure of a collection
// array containing objects
const shouldTraverse = entry =>
  (Array.isArray(entry) && entry[0] instanceof Object) ||
  (entry instanceof Object && entry[0] instanceof Object)

// check if the entry is an id
const isIdKey = key =>
  !['createdById', 'lastUpdatedById'].includes(key) &&
  (key === 'id' || key.slice(key.length - 2) === 'Id')

// check for serialized Ids
const isIdArray = (key, value) =>
  key.slice(key.length - 3, key.length) === 'Ids' && Array.isArray(value)

// traverse the passed model and update Ids where required, keeping other entries as is
const traverseModel = model =>
  Object.entries(model).reduce(
    (a, c) =>
      isIdKey(c[0])
    
        // convert id to int
        ? { ...a, [c[0]]: idToInt(c[1]) }
    
        // convert id array to int
        : isIdArray(c[0], c[1])
        ? { ...a, [c[0]]: idsToInt(c[1]) }
    
        // traverse nested entries    
        : shouldTraverse(c[1])
        ? { ...a, [c[0]]: serializeIds(c[1]) }
    
        // keep regular entries    
        : { ...a, [c[0]]: c[1] },
    {}
  )

// start traversal of data
const serializeIds = data =>
  isCollection(data)
    ? data.map(model => traverseModel(model))
    : traverseModel(data)

export default serializeIds