Firebase:Node.js：查找两个贴图对象的差异（添加或修改）

查找node.js中两个映射对象的差异的最佳方法是什么

我的地图是这样的

roles
   4K5EB8uP0G0OVWKK4YFe: "member"
   4OLEnMBAwhHL4agFD1bL: "initiate"
   Sg0igJdOusnOaDsjDGAY: "admin"
   ZQH29nwMnyHqdQvRgwd0: "initiate"
   hqmXu2I7ehhX9NyfmfdC: "initiate"
   nWX51v4HxCnznkK03rne: "initiate" 

会发生什么

• 可以添加新行（具有任何角色）
• 可以修改现有行（键将保持不变，但值将修改为任意值） 没有删除行的情况（至少还没有）。删除将把角色修改为“已删除”

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node.js中是否有“diff”方法？您可以使用

Array.filter

查找更新后

和更新前
之间的差异，如下所示：

// this one keeps all the afterUpdate keys that are not in the befoteUpdate
const addedKeys = Object.keys(afterUpdate).filter(key => !beforeUpdate[key])
// this one keeps all the afterUpdate keys related to an updated value
const modifiedKeys = Object.keys(afterUpdate).filter(key => beforeUpdate[key] && beforeUpdate[key] !== afterUpdate[key])
// note this second one excludes the afterUpdate keys that are not in the beforeUpdate because they aleady are in the addedKeys

要获取值，您可以访问
const addedValues=addedKeys.map（key=>afterUpdate[key]）

// this one keeps all the afterUpdate keys that are not in the befoteUpdate
const addedKeys = Object.keys(afterUpdate).filter(key => !beforeUpdate[key])
// this one keeps all the afterUpdate keys related to an updated value
const modifiedKeys = Object.keys(afterUpdate).filter(key => beforeUpdate[key] && beforeUpdate[key] !== afterUpdate[key])
// note this second one excludes the afterUpdate keys that are not in the beforeUpdate because they aleady are in the addedKeys