使用ramda.js的索引嵌套列表

Question

I'm learning functional programming and would appreciate any help. What would the functional equivalent of the following code be using ramda.js?

const indexArray = (array)=>{
   let idx = 0;
   return array.map((l)=>{
      return l.map((w)=>{
         let nw = { id: idx, val: w }
         idx++
         return nw
      })
   })
}

indexArray([["Hello", "World"],["Foo", "Bar"]]) 

//=> [[{"id":0,"val":"Hello"},{"id":1,"val":"World"}],[{"id":2,"val":"Foo"},{"id":3,"val":"Bar"}]] 

Answer 1

Using Scott's partial answer (thanks!) and a recursive function, I came up with the following solution. I can't help thinking there must be a more elegant way to do it, though.

const indexElements = R.pipe(R.flatten, R.addIndex(map)((val, idx) => ({idx, val})))

const lengths = R.map((l)=>l.length)

const rf = (output, input, indexes)=>{ 
  if (indexes.length == 0) return output
  let index = indexes[0]
  return rf(
    R.append(R.take(index,input), output),
    R.drop(index, input),
    R.drop(1, indexes)
  )
}

const indexNestedArray = (arr)=>rf([], indexElements(arr), lengths(arr))

indexNestedArray([["Hello", "World"],["Foo", "Bar"]])
// => [[{"idx": 0, "val": "Hello"}, {"idx": 1, "val": "World"}], [{"idx": 2, "val": "Foo"}, {"idx": 3, "val": "Bar"}]]