javascript - 数组按两次分组并计算出现次数

Question

我有以下数组:

var array = [
  { idOne: 1, oneText: 'one', idTwo: 2, twoText: 'two' },
  { idOne: 1, oneText: 'one', idTwo: 2, twoText: 'two' },
  { idOne: 12, oneText: 'twelve', idTwo: 23, twoText: 'twentythree' },
  { idOne: 12, oneText: 'twelve', idTwo: 23, twoText: 'twentythree' },
  { idOne: 12, oneText: 'twelve', idTwo: 25, twoText: 'twentyfive' },
  { idOne: 16, oneText: 'sixteen', idTwo: 56, twoText: 'fiftysix' },
  { idOne: 16, oneText: 'sixteen', idTwo: 56, twoText: 'fiftysix' },
  { idOne: 16, oneText: 'sixteen', idTwo: 56, twoText: 'fiftysix' },
  { idOne: 16, oneText: 'sixteen', idTwo: 50, twoText: 'fifty' },
  { idOne: 16, oneText: 'sixteen', idTwo: 50, twoText: 'fifty' },
  { idOne: 18, oneText: 'eighteen', idTwo: 90, twoText: 'ninety' }
];

我尝试首先按 idOne 对它们进行分组，然后按 idTwo 对它们进行分组，并计算找到了多少个，然后对它们进行排序:

我目前有以下方法:

var result = _.chain(array)
    .groupBy("idOne")
    .map(function(idOne, idOneKey) {
        return _.chain(idOne)
            .groupBy("idTwo")
            .map(function(idTwo, idTwoKey) {
                return {                
                    id: idOneKey + '-' + idTwoKey
                }
            })
            .value();
    })
    .value();

但我想返回以下数组或对象，不确定哪一个最好:

result = {
  'one-two': 2,
  'twelve-twentythree': 2,
  'twelve-twentyfive': 1,
  'sixteen-fiftysix': 3
  ...
}

它不必带有下划线或破折号，只要它起作用即可。

Answer 1

您可以使用countBy而不是 groupBy:

let result = _.countBy(array, item => item.oneText + '-' + item.twoText);