how to merge two nested objects with one taking precedence in typescript

index.ts
type NestedObject = { [key: string]: any } | NestedObject[];

function mergeNestedObjects(obj1: NestedObject, obj2: NestedObject): NestedObject {
  if (Array.isArray(obj1) || Array.isArray(obj2)) {
    // if one of the arguments is an array, concatenate them
    return [...(obj1 as any[]), ...(obj2 as any[])];
  } else {
    // otherwise, merge the objects recursively
    const mergedObject: NestedObject = { ...(obj2 as object) };
    for (const key in obj1) {
      if (obj1.hasOwnProperty(key)) {
        const value1 = obj1[key];
        const value2 = obj2[key];
        if (value2 && typeof value1 === "object" && typeof value2 === "object") {
          mergedObject[key] = mergeNestedObjects(value1, value2);
        } else {
          mergedObject[key] = value1;
        }
      }
    }
    return mergedObject;
  }
}
829 chars
24 lines

index.ts
const obj1 = {
  foo: "bar",
  nested: {
    a: true,
    b: 123,
    c: {
      d: "hello",
      e: {
        f: ["world"],
      },
    },
  },
};

const obj2 = {
  nested: {
    a: false,
    c: {
      d: "world",
      e: {
        f: ["hello"],
        g: 456,
      },
    },
  },
  extra: "property",
};

const mergedObj = mergeNestedObjects(obj1, obj2);
console.log(mergedObj);
388 chars
31 lines

index.ts
{
  "foo": "bar",
  "nested": {
    "a": true,
    "b": 123,
    "c": {
      "d": "hello",
      "e": {
        "f": ["world", "hello"],
        "g": 456
      }
    }
  },
  "extra": "property"
}
198 chars
16 lines