Recursively / deeply sort an object or array in JS

deep-sort.js

function deepSort(x, fn) {
  fn = fn || ((a, b) => (a < b ? -1 : 1))

  if (typeof x === "object") {
    if (x === null) return x

    if (x instanceof Array) {
      return x.map(v => deepSort(v, fn)).sort(fn)
    }
    
    else {
      const out = {}
      const keys = Object.keys(x).sort(fn)

      keys.forEach(key => {
        out[key] = deepSort(x[key], fn)
      })

      return out
    }
  }

  return x
}