Deeply assign JavaScript object literal

I am trying to deeply assign a value in an object. For example:

const errors = {}
if(errorOnSpecificField) {
  // TypeError: Cannot read property 'subSubCategory' of undefined(…)
  errors.subCategory.subSubCategory.fieldWithError = 'Error Message'
}

Right now, without lodash, I can do:

const errors = {}
if(errorOnSpecificField) {
    errors.subCategory = errors.SubCategory || {}
    errors.subCategory.subSubCategory = errors.SubCategory.subSubCategory || {}
    errors.subCategory.subSubCategory.fieldWithError = 'Error Message'
}

With lodash, I can do this:

const errors = {}
if(errorOnSpecificField) {
    _.set(errors, 'subCategory.subSubCategory.fieldWithError', 'Error Message');
}

I am trying to avoid using a third party library. Is there a more elegant solution, especially now that es2015 has object destructuring. The inverse operation is easy:

  let {subCategory : {subSubCategory: {fieldWithError}}} = errors

What is an elegant solution to deep object assignment? Thanks!