javascript - 从一个数组中按组获取 Sum 并将总和更新到同一组名称的另一个数组

Question

我有两个数组

levelOne = [
  {Code: "A", Count: 0, Date: 2017-04-01,....},
  {Code: "A", Count: 0, Date: 2017-05-01,....},
  {Code: "B", Count: 0, Date: 2017-04-01,....},
  {Code: "B", Count: 0, Date: 2017-05-01,....}
];    
levelTwo = [
  {Code: "A", Count: 10, Date: 2017-04-01,....},
  {Code: "A", Count: 12, Date: 2017-05-01,....},
  {Code: "B", Count: 50, Date: 2017-04-01,....},
  {Code: "B", Count: 18, Date: 2017-05-01,....},
  {Code: "A", Count: 20, Date: 2017-05-01,....},
  {Code: "B", Count: 60, Date: 2017-04-01,....},
  {Code: "B", Count: 77, Date: 2017-05-01,....}
];

我想用相同代码和日期的 levelTwo 数组中的计数总和来更新 levelOne 数组的计数。

到目前为止我做了什么？

我在 levelOne 上放置了一个 $.each 循环，但我被卡住了。

    $.each( levelOne , function( index, value ){
                  //I'm stuck
        $.each( levelTwo , function( idx, val ){
             if(value.Code==val.Code && value.Date == val.Date){
                  //I'm stuck
             }
                  //I'm stuck                
        });
    });

有什么建议吗？有更好的方法来实现吗？

Answer 1

您可以使用哈希表的相当前向的方法，首先迭代目标数组，然后迭代源数组进行计数。

通过迭代 levelOne，哈希表将填充代码和日期值作为键，对象本身作为值。

迭代levelTwo将实际的Count添加到结果数组中。

var levelOne = [{ Code: "A", Count: 0, Date: '2017-04-01' }, { Code: "A", Count: 0, Date: '2017-05-01' }, { Code: "B", Count: 0, Date: '2017-04-01' }, { Code: "B", Count: 0, Date: '2017-05-01' }],
    levelTwo = [{ Code: "A", Count: 10, Date: '2017-04-01' }, { Code: "A", Count: 12, Date: '2017-05-01' }, { Code: "B", Count: 50, Date: '2017-04-01' }, { Code: "B", Count: 18, Date: '2017-05-01' }, { Code: "A", Count: 20, Date: '2017-05-01' }, { Code: "B", Count: 60, Date: '2017-04-01' }, { Code: "B", Count: 77, Date: '2017-05-01' }],
    getKey = function (o) { return ['Code', 'Date'].map(function (k) { return o[k]; }).join('|'); },
    hash = Object.create(null);

levelOne.forEach(function (o) { hash[getKey(o)] = o; });
levelTwo.forEach(function (o) { hash[getKey(o)].Count += o.Count; });
   
console.log(levelOne);

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ES6 带有 Map

var levelOne = [{ Code: "A", Count: 0, Date: '2017-04-01' }, { Code: "A", Count: 0, Date: '2017-05-01' }, { Code: "B", Count: 0, Date: '2017-04-01' }, { Code: "B", Count: 0, Date: '2017-05-01' }],
    levelTwo = [{ Code: "A", Count: 10, Date: '2017-04-01' }, { Code: "A", Count: 12, Date: '2017-05-01' }, { Code: "B", Count: 50, Date: '2017-04-01' }, { Code: "B", Count: 18, Date: '2017-05-01' }, { Code: "A", Count: 20, Date: '2017-05-01' }, { Code: "B", Count: 60, Date: '2017-04-01' }, { Code: "B", Count: 77, Date: '2017-05-01' }],
    hash = new Map,
    getKey = o => ['Code', 'Date'].map(k => o[k]).join('|');

levelOne.forEach(o => hash.set(getKey(o), o));
levelTwo.forEach(o => hash.get(getKey(o)).Count += o.Count);
   
console.log(levelOne);

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