Ramda deep merge.

deepMerge.js

var R = require('ramda')

var one = {
  test: {
    a: 1,
    b: 2
  },
  pemento: "sipi",
  arr: ['a', 'b']
}

var two = {
  test: {
    a:3,
    c:4
  },
  pemento: "nope",
  arr: ['b', 'c']
}

function deepMerge(v1, v2) {
  if(Array.isArray(v1) && Array.isArray(v2)) {
    return R.uniq(R.concat(v1, v2));
  }
  else if(typeof v1 === 'object' && typeof v2 === 'object'){
    return R.mergeWith(deepMerge, v1, v2)
  }
  else {
    return v2;
  }
}

R.mergeWith(deepMerge,one, two)

The second if statement should also check if v1 and v2 are null, because typeof null === 'object'.

function deepMerge(v1, v2) {
  if(Array.isArray(v1) && Array.isArray(v2)) {
    return R.uniq(R.concat(v1, v2));
  }
  else if(typeof v1 === 'object' && typeof v2 === 'object' && !R.isNil(v1) && !R.isNil(v2)){
    return R.mergeWith(deepMerge, v1, v2)
  }
  else {
    return v2;
  }
}