javascript - JS中根据一个属性值提取列表

Question

我有这样的对象:

input = [  {value: 1,
    week: 1,
    year: 2017
   },
   {value: 10,
    week: 30;
    year: 2018
   },
   {value: 2,
    week: 2,
    year: 2018
   },
   {value:3,
    week: 3,
    year: 2017
   }
]

我想获得这个对象:

{ 2017: {value : [1, 3],
         week: [1, 3]
        },
  2018: {value : [10, 2],
         week: [30, 2]
        }
}

我从 _.groupBy(input, function(elem) {return elem.year}) 开始，但后来我卡住了。

Answer 1

你可以使用.reduce

let input = [{
    value: 1,
    week: 1,
    year: 2017
  },
  {
    value: 10,
    week: 30,
    year: 2018
  },
  {
    value: 2,
    week: 2,
    year: 2018
  },
  {
    value: 3,
    week: 3,
    year: 2017
  }
];

let result = input.reduce((c, v) => {
  c[v.year] = c[v.year] || {value: [], week: []};
  c[v.year].value.push(v.value);
  c[v.year].week.push(v.value);
  return c;
}, {});

console.log(result);

文档:https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/Array/reduce