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

More general solution below. It makes recursively assigning only if there are conflicts (same key names). It resolves issues assigning complex objects, which has many reference points. For example, nested-object-assign, an existing package for nested object assign in npm, stuck with complex objects assign because it recursively goes through all keys.

var objecttarget = {
  a: 'somestring',
  b: {x:2,y:{k:1,l:1},z:{j:3,l:4}},
  c: false
};

var objectsource = {
  a: 'somestring else',
  b: {k:1,x:2,y:{k:2,p:1},z:{}},
  c: true
};

function nestedassign(target, source) {
  Object.keys(source).forEach(sourcekey=>{
    if (Object.keys(source).find(targetkey=>targetkey===sourcekey) !== undefined && typeof source[sourcekey] === "object") {
      target[sourcekey]=nestedassign(target[sourcekey],source[sourcekey]);
    } else {
      target[sourcekey]=source[sourcekey];
    }
  });
  return target;
}

// It will lose objecttarget.b.y.l and objecttarget.b.z
console.log(Object.assign(Object.create(objecttarget),objectsource));

// Improved object assign
console.log(nestedassign(Object.create(objecttarget),objectsource));