将 2 个对象数组与下划线进行比较以找出差异答案

【问题标题】：Compare 2 arrays of objects with Underscore to find the differnce将 2 个对象数组与下划线进行比较以找出差异
【发布时间】：2020-11-13 01:44:35
【问题描述】：

我有 2 个数组，一个是 newVal，另一个是 origVal define

原件：

[
{"ListingId":1762276,"Rating":3,"ListPrice":7411828,"PropertyType":"Residential"},
{"ListingId":1826692,"Rating":3,"ListPrice":650000,"PropertyType":"Residential"},
{"ListingId":1833283,"Rating":4,"ListPrice":950000,"PropertyType":"Residential"},
{"ListingId":1832134,"Rating":3,"ListPrice":850000,"PropertyType":"Residential"},
{"ListingId":1829932,"Rating":4,"ListPrice":750000,"PropertyType":"Residential"},
{"ListingId":1827548,"Rating":5,"ListPrice":650000,"PropertyType":"Residential"}
]

新：

[
{"ListingId":1762276,"Rating":2,"ListPrice":7411828,"PropertyType":"Residential"},
{"ListingId":1826692,"Rating":3,"ListPrice":650000,"PropertyType":"Residential"},
{"ListingId":1833283,"Rating":4,"ListPrice":950000,"PropertyType":"Residential"},
{"ListingId":1832134,"Rating":3,"ListPrice":850000,"PropertyType":"Residential"},
{"ListingId":1829932,"Rating":4,"ListPrice":750000,"PropertyType":"Residential"},
{"ListingId":1827548,"Rating":5,"ListPrice":650000,"PropertyType":"Residential"}
]

如果我更改新的评级之一，我如何检测到该更改并检索更改的对象？

一次只会有一个变化，虽然我认为这并不重要。

仅供参考：这些数组是由 Anjularjs watchcollection 生成的

$scope.$watchCollection('items', function (new, old) {

}, true);

谢谢，斯蒂芬

【问题讨论】：

这些是数组中的相同对象（即===身份）还是只是看起来相似？
你需要什么结果？更改对象在数组中的索引，新更改对象，旧更改对象，评分？
我更喜欢更改后的对象，即 {"ListingId":1762276,"Rating":2,"ListPrice":7411828,"PropertyType":"Residential"}

标签： javascript underscore.js

【解决方案1】：

看看这个：

var a = [
{"ListingId":1762276,"Rating":3,"ListPrice":7411828,"PropertyType":"Residential"},
{"ListingId":1826692,"Rating":3,"ListPrice":650000,"PropertyType":"Residential"},
{"ListingId":1833283,"Rating":4,"ListPrice":950000,"PropertyType":"Residential"},
{"ListingId":1832134,"Rating":3,"ListPrice":850000,"PropertyType":"Residential"},
{"ListingId":1829932,"Rating":4,"ListPrice":750000,"PropertyType":"Residential"},
{"ListingId":1827548,"Rating":5,"ListPrice":650000,"PropertyType":"Residential"}
];

var b = [
{"ListingId":1762276,"Rating":2,"ListPrice":7411828,"PropertyType":"Residential"},
{"ListingId":1826692,"Rating":3,"ListPrice":650000,"PropertyType":"Residential"},
{"ListingId":1833283,"Rating":4,"ListPrice":950000,"PropertyType":"Residential"},
{"ListingId":1832134,"Rating":3,"ListPrice":850000,"PropertyType":"Residential"},
{"ListingId":1829932,"Rating":4,"ListPrice":750000,"PropertyType":"Residential"},
{"ListingId":1827548,"Rating":5,"ListPrice":650000,"PropertyType":"Residential"}
]

var difference = function(array){
   var rest = Array.prototype.concat.apply(Array.prototype, Array.prototype.slice.call(arguments, 1));

   var containsEquals = function(obj, target) {
    if (obj == null) return false;
    return _.any(obj, function(value) {
      return _.isEqual(value, target);
    });
  };

  return _.filter(array, function(value){ return ! containsEquals(rest, value); });
};

console.log(JSON.stringify(difference(b, a)));
> [{"ListingId":1762276,"Rating":2,"ListPrice":7411828,"PropertyType":"Residential"}]

代码基于下划线的原始函数difference，但它使用isEqual在对象之间进行深度比较。

【讨论】：

太棒了，它的作用。我希望我能理解代码。

【解决方案2】：

如果顺序没有改变，一个简单的迭代就可以了。下划线为此任务提供find method：

var changedObj = _.find(newVal, function(obj, index) {
    return obj.Rating != oldVal[index].Rating;
});

【讨论】：

【解决方案3】：

怎么样：

const current = [{name:'a'},{name:'b'},{name:'c'}]
const update = [{name:'x'},{name:'a'},{name:'b'},{name:'f'}]
const records = current.concat(update);
const diff = {};
diff.in = []
diff.out = [];
records.forEach(item => {
  if(!current.find(cur => item.name == cur.name))diff.in.push(item)
  if(!update.find(up => item.name == up.name ))diff.out.push(item)
})

【讨论】：

【解决方案4】：

基于@Jonathan 的回答，我调整了一个版本，该版本返回一个可用的差异列表，包括哪一方有差异和记录的索引。

var a = [
{"ListingId":1762276,"Rating":3,"ListPrice":7411828,"PropertyType":"Residential"},
{"ListingId":1826692,"Rating":3,"ListPrice":650000,"PropertyType":"Residential"},
{"ListingId":1833283,"Rating":4,"ListPrice":950000,"PropertyType":"Residential"},
{"ListingId":1832134,"Rating":3,"ListPrice":850000,"PropertyType":"Residential"},
{"ListingId":1829932,"Rating":4,"ListPrice":750000,"PropertyType":"Residential"},
{"ListingId":1827548,"Rating":5,"ListPrice":650000,"PropertyType":"Residential"}
];

var b = [
{"ListingId":1762276,"Rating":2,"ListPrice":7411828,"PropertyType":"Residential"},
{"ListingId":1826692,"Rating":3,"ListPrice":650000,"PropertyType":"Residential"},
{"ListingId":1833283,"Rating":4,"ListPrice":950000,"PropertyType":"Residential"},
{"ListingId":1832131,"Rating":3,"ListPrice":850000,"PropertyType":"Residential"},
{"ListingId":1829932,"Rating":4,"ListPrice":750000,"PropertyType":"Residential"},
{"ListingId":1827548,"Rating":5,"ListPrice":650000,"PropertyType":"Residential"}
]

function diff(arr1, arr2){
    var aDiffs=[]
    function __comp(arrL, arrR, side){
        var rL, rR, bFound
        for(var i=0;i<arrL.length;i++){rL=arrL[i]
            bFound=false
            for(var j=0;j<arrR.length;j++){rR=arrR[j]
                if (_.isEqual(rL, rR)){ 
                    bFound=true
                    break
                }
            }
            if (!bFound)aDiffs.push({side: side, ind: i, obj: rL})
        }
    }
    __comp(arr1, arr2, 'l')
    __comp(arr2, arr1, 'r')
    return aDiffs
};


console.log(JSON.stringify(diff(b, a)).replace(/},{/g, "}\n,{"));

输出：

[{"side":"l","ind":0,"obj":{"ListingId":1762276,"Rating":2,"ListPrice":7411828,"PropertyType":"Residential"}}
,{"side":"l","ind":3,"obj":{"ListingId":1832131,"Rating":3,"ListPrice":850000,"PropertyType":"Residential"}}
,{"side":"r","ind":0,"obj":{"ListingId":1762276,"Rating":3,"ListPrice":7411828,"PropertyType":"Residential"}}
,{"side":"r","ind":3,"obj":{"ListingId":1832134,"Rating":3,"ListPrice":850000,"PropertyType":"Residential"}}]

【讨论】：