Question

我有以下内容：

[
{year: 2017, week: 45},
{year: 2017, week: 46},
{year: 2017, week: 47},
{year: 2017, week: 48},
{year: 2017, week: 50},
{year: 2017, week: 52},
{year: 2018, week: 1},
{year: 2018, week: 2},
{year: 2018, week: 5}
]

但是希望按年将其分组为以下格式：

[
  { 2017 : [{
     label: 45, value: 45,
     label: 46, value: 46,
     label: 47, value: 47,
     label: 48, value: 48,
     etc
  },
  { 2018 : [{
     label: 1, value: 1,
     label: 2, value: 2,
     etc
  }]
]

使用Javascript（ES6）执行此操作的最佳方法是什么？我也可以使用lodash / underscore库。

Answer 1

使用reduce

var output = arr.reduce((a, b) => ((a[b.year] = a[b.year] || []).push({
  label: b.week,
  val: b.week
}), a), {});

<强>演示

＆＃13;

var arr = [{
    year: 2017,
    week: 45
  },
  {
    year: 2017,
    week: 46
  },
  {
    year: 2017,
    week: 47
  },
  {
    year: 2017,
    week: 48
  },
  {
    year: 2017,
    week: 50
  },
  {
    year: 2017,
    week: 52
  },
  {
    year: 2018,
    week: 1
  },
  {
    year: 2018,
    week: 2
  },
  {
    year: 2018,
    week: 5
  }
];

var output = arr.reduce((a, b) => (a[b.year] = a[b.year] || [], a[b.year].push({
  label: b.week,
  val: b.week
}), a), {});

console.log(output);

＆＃13;

Answer 2

您可以使用哈希表并使用对数组的引用来插入新对象。

var data = [{ year: 2017, week: 45 }, { year: 2017, week: 46 }, { year: 2017, week: 47 }, { year: 2017, week: 48 }, { year: 2017, week: 50 }, { year: 2017, week: 52 }, { year: 2018, week: 1 }, { year: 2018, week: 2 }, { year: 2018, week: 5 }],
    hash = Object.create(null),
    result = [];

data.forEach(function (o) {
    var temp = {};
    if (!hash[o.year]) {
        hash[o.year] = [];
        temp[o.year] = hash[o.year];
        result.push(temp);
    }
    hash[o.year].push({ label: o.week, value: o.week });
});

console.log(result);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 3

它会对你有所帮助

var arr=[
{year: 2017, week: 45},
{year: 2017, week: 46},
{year: 2017, week: 47},
{year: 2017, week: 48},
{year: 2017, week: 50},
{year: 2017, week: 52},
{year: 2018, week: 1},
{year: 2018, week: 2},
{year: 2018, week: 5}
]
var groupBy = function(xs, key) {
    return xs.reduce(function(rv, x) {
       (rv[x[key]] = rv[x[key]] || []).push(x);
         return rv;
    }, {});
};
var arr_res=groupBy(arr, 'year')
console.log(arr_res);

Answer 4

您可以使用.reduce和Array.from：

我已经对您的要求做出了假设，因为您要求的内容不是有效对象。

const res = Array.from(arr.reduce((accum, val) => {
  const grouping = accum.get(val.year) || [];
  grouping.push({ label: val.week, value: val.week });
  accum.set(val.year, grouping);
  return accum;
}, new Map()), kv => ({ [kv[0]]: kv[1] }));

console.log(JSON.stringify(res, null, 2));

Array.from

分组数组值Javascript

4 个答案: