如何比较两个对象并删除重复项？

Question

例如：

let old = {user1: {name:'Felix', balance:1000},
                  user2: {name:'Marques', balance:3000}}
let new = {user1: {name:'Felix', balance:1000},
                  user2: {name:'Marques', balance:2000}}

唯一改变的是 user2 的余额，所以我怎样才能得到这样的输出：

{user2: {balance:2000}}

Answer 1

由于您要比较的对象具有一定的深度（内部对象），您可以递归循环并建立差异。下面的代码似乎可以完成这项工作。

let old = {user1: {name:'Felix', balance:1000},
                  user2: {name:'Marques', balance:3000, missing: 7}}
let newer = {user1: {name:'Felix', balance:1000},
                  user2: {name:'Marques', balance:2000, extra: 7}}
                  
const findDiff = (o1, o2) => {
  let diff;
  for (const key in o1) {
    const obj1 = o1[key]
    const obj2 = o2 === undefined? o2 : o2[key]
    if (typeof obj1 === 'object') {
      // recursively call if it's an object 
      // unless we know it's undefined in o2 already
      if (obj2 === undefined) diff[key] = obj2
      else {
        const subDiff = findDiff(obj1,obj2)
        // if there's a difference, add it to the diff object
        if (subDiff !== undefined) {
          if (!diff) diff = {}
          diff[key] = subDiff
        }
      }
    } else if (obj1 !== obj2) {
      // for non-objects add to the diff object if different
      diff = {[key]: obj2}
    }
  }
  for (const key in o2) {
    // any keys in o2 that weren't in o1 are also differences
    if (!o1.hasOwnProperty(key)) {
      if (!diff) diff = {}
      diff[key] = o2[key]
    }
  }
  return diff
}

console.log(findDiff(old,newer))