flatten nested object with topairs in lodash

Question

I have an object like this:

let order={
  "john":{
    "hamburger":4
  },
  "alice":{
    "pizza":10,
    "milkshake":2
  },
  "bob":{
  }
}

that I would like to flatten like this:

let res=[
   ["john","hamburger",4],

   ["alice","pizza",4],
   ["alice","milkshake",4]

]

I know how to do it in reverse, using keyBy but how can I turn it from a recursive object to a recursive array? I tried using toPairs, but I can't figure out how to make it recursive

Answer 1

Use _.toPairs() to get an array of [name, items] pairs, which you iterate with _.flatMap(). Get the pairs from the items object, and use _.map() to create the arrays that include the info:

const { flatMap, toPairs, map } = _

const order = {"john":{"hamburger":4},"alice":{"pizza":10,"milkshake":2},"bob":{}}

const result = flatMap(
  toPairs(order),
  ([name, items]) => 
    map(
      toPairs(items),
      ([product, price]) => [name, product, price]
    )
)

console.log(result)

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In vanilla JS you can use Array.flatMap() with Object.entries() to get the same result:

const order = {"john":{"hamburger":4},"alice":{"pizza":10,"milkshake":2},"bob":{}}

const result = Object
  .entries(order)
  .flatMap(([name, items]) =>
    Object.entries(items)
      .map(([product, price]) => [name, product, price])
  )

console.log(result)