在JavaScript中按字符串属性值对对象数组进行分组？

Question

我讨厌这个对象数组，每个对象都有一个日期，我希望能够将这些对象分组到月份。有没有一种方法可以将其转换为：

var data  = [
  { date: "2016-08-13",...},
  { date: "2016-07-23",...},
  { date: "2016-08-11",...},
  { date: "2016-08-10",...},
  { date: "2016-07-20",...},
  { date: "2016-07-21",...},
]

将其转换为类似这样的形式

var data  = [
  [{ date: "2016-08-13",...},
  { date: "2016-08-11",...},
  { date: "2016-08-10",...}],
  [{ date: "2016-07-20",...},
  { date: "2016-07-21",...},
  { date: "2016-07-23",...}[
]

- relidon

---

可能是重复的问题：什么是在 JavaScript 对象数组上进行 groupby 的最有效方法？ - Andreas

Answer 1

你可以在哈希表中获取年份和月份组成的一部分字符串，并为每个组新建一个数组，将这些数组放入结果集中。

var data = [{ date: "2016-08-13" }, { date: "2016-07-23" }, { date: "2016-08-11" }, { date: "2016-08-10" }, { date: "2016-07-20" }, { date: "2016-07-21" }],
    hash = Object.create(null),
    result = [];

data.forEach(function (o) {
    var key = o.date.slice(0, 7);
    if (!hash[key]) {
        hash[key] = [];
        result.push(hash[key]);
    }
    hash[key].push(o);
});

console.log(result);

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- Nina Scholz

---

为什么要使用 hash = Object.create(null)，而不是 hash={}？ - mplungjan

@mplungjan，它创建了一个没有原型的空对象，就像toString（如果这是哈希的值，它可以在检查时为true，但它不支持数组）。 - Nina Scholz

我知道了。那是一个新的。它比“{}”要小得多。 - mplungjan

Answer 2

你可以使用数组#reduce按月份对对象进行分组。

var data  = [{ date: "2016-08-13"},{ date: "2016-07-23"},{ date: "2016-08-11"},{ date: "2016-08-10"},{ date: "2016-07-20"},{ date: "2016-07-21"}];

var result = data.reduce((res,obj) => {
  let [year, month, day] = obj.date.split('-');
  if(res[month])
    res[month].push(obj);
  else
    res[month] = [obj];
  return res;
},{});
console.log(Object.values(result));

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var data  = [{ date: "2016-08-13"},{ date: "2016-07-23"},{ date: "2016-08-11"},{ date: "2016-08-10"},{ date: "2016-07-20"},{ date: "2016-07-21"}];

var result = data.reduce((res,obj) => {
  let [year, month, day] = obj.date.split('-');
  res[month] = res[month] || [];
  res[month].push(obj);
  return res;
},{});
console.log(Object.values(result));

- Hassan Imam

Answer 3

按月分组：

var groupedData = [];

for(i=0;i<12;i++)
   groupedData.push([]);

for(var index = 0;index<data.length;index++){
   var date = new Date(data[index].date);
   groupedData[date.getMonth()] = data[index];
}

- Naveen

Answer 4

var data  = [
{ date: "2016-08-13"},
{ date: "2016-07-23"},
{ date: "2016-08-11"},
{ date: "2016-08-10"},
{ date: "2016-07-20"},
{ date: "2016-07-21"}
];

var monthDateIndex = {
 "01": "Jan",
 "02" : "Feb",
 "03" : "mar",
 "04" : "april",
 "05" : "may",
 "06" : "june",
 "07" : "july",
 "08" : "august",
 "09" : "sept",
 "10" : "oct",
 "11" : "nov",
 "12" : "dec"
}

let newDataObj = [];
Object.keys(monthDateIndex).map(monthNum => {
        let monthObj = [];
   data.map(dateObj => {   
       if(monthNum == dateObj.date.split("-")[1]) {
        monthObj.push(dateObj);
     }
   });
   if(monthObj.length != 0) newDataObj.push(monthObj);
});

- Rajkumar Somasundaram

Answer 5

var data  = [
  { date: "2016-08-13"},
  { date: "2016-07-23"},
  { date: "2016-08-11"},
  { date: "2016-08-10"},
  { date: "2016-07-20"},
  { date: "2016-07-21"},
];

data.sort(function(a, b) {
  var aDate = new Date(a.date);
  var bDate = new Date(b.date);
  return bDate - aDate;
});

console.log(data);

- pmaddi