R.lens* and R.cond are best friends!

utils.js

import R from 'ramda'

export const getFormData = R.pipe(
  (form) => [...(new FormData(form)).entries()],
  R.reduce(
    (a, [k, v]) => {
      const kL = R.lensProp(k)
      return R.cond([
        [R.pipe(R.view(kL), R.isNil), R.set(kL, v)],
        [R.pipe(R.view(kL), R.isArrayLike), R.over(kL, R.append(v))],
        [R.T, R.over(kL, (x) => [x, v])]
      ])(a)
    },
    {}
  )
)