javascript - 使用 Lodash 将最后一个树节点合并到数组中

Question

场景:

const obj1 = {
  a: 100,
  b: 200,
  c: { c1: 100 }
}

const obj2 = {
  b: 250,
  c: { c1: 200 },
  d: { d1: { d1a: 400 } }
}

期望的结果:

someMergeFn(obj1, obj2)

// Should return...

{
  a: [100],
  b: [200, 250],
  c: { c1: [100, 200] },
  d: { d1: { d1a: [400] } }
}

---

我的尝试如下，但我无法接近预期的结果。

const obj1 = {
  a: 100,
  b: 200,
  c: { c1: 100 }
}

const obj2 = {
  b: 250,
  c: { c1: 200 },
  d: { d1: { d1a: 400 } }
}

const merged = _.mergeWith(
  obj1,
  obj2,
  (first, second) =>
    Array.isArray(first) ? first.push(second) : [first, second]
)

console.log(merged)

<script src="https://cdn.jsdelivr.net/npm/<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="aec2c1cacfddc6ee9a809f99809f9b" rel="noreferrer noopener nofollow">[email protected]</a>/lodash.min.js"></script>

Answer 1

使用空对象开始合并。这将防止第一个对象发生突变，并将所有值开始为空，在这种情况下，我们将提供一个空数组作为 first 的默认值。

只要第二个值不是对象(或数组)，我们就可以假设第一个值是数组，并使用展开(或连接)将它们组合成一个新数组。如果没有，我们返回undefined，以便_.mergeWith() 处理对象/数组的合并。

const obj1 = {"a":100,"b":200,"c":{"c1":100}}
const obj2 = {"b":250,"c":{"c1":200},"d":{"d1":{"d1a":400}}}

const merged = _.mergeWith(
  {},
  obj1,
  obj2,
  (first, second) =>
    !_.isObject(second) ? [...(first || []), second] : undefined
)

console.log(merged)

<script src="https://cdn.jsdelivr.net/npm/<a href="https://stackoverflow.com/cdn-cgi/l/email-protection" class="__cf_email__" data-cfemail="264a494247554e6612081711081713" rel="noreferrer noopener nofollow">[email protected]</a>/lodash.min.js"></script>