将重复属性值汇总为新对象

Question

我试图总结出现在如下构造的对象数组中的值：

[ 
  { token: 'N97235', conversions: '2', payout: '100' },
  { token: 'N91567', conversions: '2', payout: '100' },
  { token: 'N91567', conversions: '3', payout: '150' },
  { token: 'N97759', conversions: '2', payout: '100' },
  { token: 'N97240', conversions: '1', payout: '50' },
  { token: 'N13925', conversions: '1', payout: '50' },
  { token: 'N53285', conversions: '1', payout: '50' },
  { token: 'N28312', conversions: '1', payout: '100' },
  { token: 'N96475', conversions: '1', payout: '50' },
  { token: 'N97759', conversions: '2', payout: '100' },
  { token: 'N76951', conversions: '1', payout: '100' },
  { token: 'N39108', conversions: '1', payout: '50' },
  { token: 'N39108', conversions: '4', payout: '200' },
  { token: 'N48854', conversions: '2', payout: '100' },
  { token: 'N50179', conversions: '1', payout: '50' },
  { token: 'N18804', conversions: '1', payout: '50' },
  { token: 'N95631', conversions: '2', payout: '100' },
]

我的意思是，我想把所有的转换和支出相加到一个新的对象中，如下所示

{
  N97235: { conversions: 2, payout: 100 },
  N39108: { conversions: 5, payout: 250 },
  N91567: { conversions: 6, payout: 300},
  N96475: { conversions: 1, payout: 50},
  // ..and so on
}

正如您所看到的，它在原始数组中找到了重复的“条目”，并将它们的转换和支出相加到一个新对象中(单个条目也在其中)。我试图做的是遍历这个数组(在本例中是tokens_array[])，并将其‘objects’属性附加到新创建的对象( conversions_sum{} one)，但问题是在向其添加任何内容之前，首先对其值进行“空化”。

tokens_array.forEach(function(element) {
    var token_string = element.token.toString();
    conversions_sum[token_string] = {};
    conversions_sum[token_string].conversions += element.conversions;
    conversions_sum[token_string].payout += element.payout;
});

但是，由于conversions_sumtoken_string.conversions和conversions_sumtoken_string.payout从一开始就没有初始化--它将这个数字添加到“未定义”中。

提前谢谢。

Answer 1

您可以使用Array.prototype.reduce创建令牌的散列对象，如下所示：

​

function group(arr) {
  return arr.reduce(function(h, e) {             // for each object e in arr
    if(h[e.token]) {                             // if we already hashed the object
      h[e.token].conversions += +e.conversions;  // add e's conversions to the hashed object (implicitly convert e.conversions into a number using unary +)
      h[e.token].payout += +e.payout;            // add e's payout to the hashed object as well
    }                                            
    else {                                       // if not, then create a new object initialized with e's values
      h[e.token] = {conversions: +e.conversions, payout: +e.payout};
    }

    return h;
  }, {});
}

var array = [ 
  { token: 'N97235', conversions: '2', payout: '100' },
  { token: 'N91567', conversions: '2', payout: '100' },
  { token: 'N91567', conversions: '3', payout: '150' },
  { token: 'N97759', conversions: '2', payout: '100' },
  { token: 'N97240', conversions: '1', payout: '50' },
  { token: 'N13925', conversions: '1', payout: '50' },
  { token: 'N53285', conversions: '1', payout: '50' },
  { token: 'N28312', conversions: '1', payout: '100' },
  { token: 'N96475', conversions: '1', payout: '50' },
  { token: 'N97759', conversions: '2', payout: '100' },
  { token: 'N76951', conversions: '1', payout: '100' },
  { token: 'N39108', conversions: '1', payout: '50' },
  { token: 'N39108', conversions: '4', payout: '200' },
  { token: 'N48854', conversions: '2', payout: '100' },
  { token: 'N50179', conversions: '1', payout: '50' },
  { token: 'N18804', conversions: '1', payout: '50' },
  { token: 'N95631', conversions: '2', payout: '100' },
];

console.log(group(array));

​

Answer 2

那么，初始化它们，对吗？您也每次都要重写新对象，但只希望在不存在新对象时覆盖它。就像这样：

 conversions_sum[token_string] = conversions_sum[token_string] || {
   conversions: 0,
   payout: 0
 };
conversions_sum[token_string].conversions += parseInt(element.conversions, 10);
conversions_sum[token_string].payout += parseInt(element.payout, 10);