Function deepMerger

src/functional/merge.js:78–86

(oldValue, newValue, key)

function deepMergerWith(merger) {
  function deepMerger(oldValue, newValue, key) {
    return isDataStructure(oldValue) &&
      isDataStructure(newValue) &&
      areMergeable(oldValue, newValue)
      ? mergeWithSources(oldValue, [newValue], deepMerger)
      : merger
        ? merger(oldValue, newValue, key)
        : newValue;
  }
  return deepMerger;
}