So optimieren Sie die JSON-Datengruppierung in JS

[
 {"date":"2017-12-22","start_time":"10:00:00","end_time":"10:00:00","status":"Performance Time"},
 {"date":"2017-12-22","start_time":"10:40:00","end_time":"10:40:00","status":"Performance Time"},
 {"date":"2017-12-23","start_time":"10:00:00","end_time":"10:00:00","status":"Performance Time"},
 {"date":"2017-12-23","start_time":"10:40:00","end_time":"10:40:00","status":"Performance Time"}
]

[
 {
 date: '2017-12-22',
 data: [
  {
  date: '2017-12-22',
  start_time: '10:00:00',
  end_time: '10:00:00',
  status: 'Performance Time'
  },
  {
  date: '2017-12-22',
  start_time: '10:40:00',
  end_time: '10:40:00',
  status: 'Performance Time'
  }
 ]
 },
 {
 date: '2017-12-23',
 data: [
  {
  date: '2017-12-23',
  start_time: '10:00:00',
  end_time: '10:00:00',
  status: 'Performance Time'
  },
  {
  date: '2017-12-23',
  start_time: '10:40:00',
  end_time: '10:40:00',
  status: 'Performance Time'
  }
 ]
 }
]

var map = {},
 nList = []
 //遍历原始数组
 for (var i = 0; i < arr.length; i++) {
 var item = arr[i]
 //如果map没有则在新nList中添加
 if (!map[item.date]) {
  nList.push({
  date: item.date,
  data: [item]
  })
  map[item.date] = item
 } else {
  //遍历nList
  for (var j = 0; j < nList.length; j++) {
  var nItem = nList[j]、
  //如查找到date符合则添加
  if (nItem.date == item.date) {
   nItem.data.push(item)
   //跳出循环
   break
  }
  }
 }
 }

let map = {},
 nList = []
 arr.forEach((item) => {
 if (!map[item.date]) {
  nList.push({
  date: item.date,
  data: [item]
  })
  map[item.date] = item
 } else {
  //因为forEach不支持break，所以使用every实现
  nList.every((nItem) => {
  if (nItem.date === item.date) {
   nItem.data.push(item)
   return false
  }
  return true
  })
 }
 })

let map = {},
 nList = []
 //设置初始key为0
 let _nkey = 0
 arr.forEach((item, index) => {
 if (index === 0) {
  nList.push({
  date: item.date,
  data: [item]
  })
 } else {
  let oItem = arr[index - 1]
  //和前一个date一致则在当前添加，否则添加至nList
  if (item.date === oItem.date) {
  nList[_nkey]['data'].push(item)
  } else {
  nList.push({
   date: item.date,
   data: [item]
  })
  _nkey ++
  }
 }
 })

var o={"xlid":"cxh","xldigitid":123456,"topscore":2000,"topplaytime":"2009-08-20"}；

  var jsonranklist=[{"xlid":"cxh","xldigitid":123456,"topscore":2000,"topplaytime":"2009-08-20"},{"xlid":"zd","xldigitid":123456,"topscore":1500,"topplaytime":"2009-11-20"}];

  var str1 = '{ "name": "cxh", "sex": "man" }';

 var str2 = { "name": "cxh", "sex": "man" };

  //由JSON字符串转换为JSON对象
var obj = eval('(' + str + ')');

var obj = str.parseJSON(); //由JSON字符串转换为JSON对象

  var obj = JSON.parse(str); //由JSON字符串转换为JSON对象

  Alert(obj.name);
  Alert(obj.sex);

var last=obj.toJSONString(); //将JSON对象转化为JSON字符

  var last=JSON.stringify(obj); //将JSON对象转化为JSON字符
  alert(last);