Object.assign—override nested property

Question

I have an Object a like that:

const a = {
  user: {
   …
   groups: […]
   …
  }
}

whereby there are a lot more properties in

Answer 1

Here's a small function called Object_assign (just replace the . with a _ if you need nested assigning)

The function sets all target values by either pasting the source value in there directly, or by recursively calling Object_assign again when both the target value and source value are non-null objects.

const target = {
  a: { x: 0 },
  b: { y: { m: 0, n: 1      } },
  c: { z: { i: 0, j: 1      } },
  d: null
}

const source1 = {
  a: {},
  b: { y: {       n: 0      } },
  e: null
}

const source2 = {
  c: { z: {            k: 2 } },
  d: {}
}

function Object_assign (target, ...sources) {
  sources.forEach(source => {
    Object.keys(source).forEach(key => {
      const s_val = source[key]
      const t_val = target[key]
      target[key] = t_val && s_val && typeof t_val === 'object' && typeof s_val === 'object'
                  ? Object_assign(t_val, s_val)
                  : s_val
    })
  })
  return target
}

console.log(Object_assign(Object.create(target), source1, source2))