如何创建一个唯一的 json 对象数组并在字段上排序？

Question

如何在公共 id 上填充以下数组并且输出应该具有唯一且最新的历史记录编号

const input = [{
  "id": 134116,
  "user": "admin",
  "historyno": "134116-0"
}, {
  "id": 134132,
  "user": "admin",
  "historyno": "134132-0"
}, {
  "id": 134132,
  "user": "admin",
  "historyno": "134132-1"
}, {
  "id": 134133,
  "user": "admin",
  "historyno": "134133-0"
}, {
  "id": 134133,
  "user": "admin",
  "historyno": "134133-1"
}];

let output = [];
let tempId;

for (let i = 0; i < input.length; i++) {
  if (input[i].id === tempId) {
    //do nothing
  } else {
    output.push(input[i]);
    tempId = input[i].id;
  }
}

console.log(output);

预期输出

[
  {
    "id": 134116,
    "user": "admin",
    "historyno": "134116-0"
  },
  {
    "id": 134132,
    "user": "admin",
    "historyno": "134132-1"
  },
  {
    "id": 134133,
    "user": "admin",
    "historyno": "134133-1"
  }
]

Answer 1

将数组缩减为 Map，使用 id 作为键，然后通过将 Map.values() 迭代器传播到数组来转换回数组。

此解决方案假定数组已按历史编号预排序：

const input = [{"id":134116,"user":"admin","historyno":"134116-0"},{"id":134132,"user":"admin","historyno":"134132-0"},{"id":134132,"user":"admin","historyno":"134132-1"},{"id":134133,"user":"admin","historyno":"134133-0"},{"id":134133,"user":"admin","historyno":"134133-1"}];

const output = [...input.reduce((r, o) => r.set(o.id, o), new Map).values()];

console.log(output);

如果 historyno 大于：

，此解决方案通过仅替换映射中的当前项来处理未排序的数组

const input = [{"id":134116,"user":"admin","historyno":"134116-0"},{"id":134132,"user":"admin","historyno":"134132-0"},{"id":134132,"user":"admin","historyno":"134132-1"},{"id":134133,"user":"admin","historyno":"134133-0"},{"id":134133,"user":"admin","historyno":"134133-1"}];

const getHistoryNo = ({ historyno }) => +historyno.split('-')[1];

const output = [...input.reduce((r, o) => {
  const prev = r.get(o.id);
  
  if(!prev || getHistoryNo(o) > getHistoryNo(prev)) r.set(o.id, o);
  
  return r;
}, new Map).values()];

console.log(output);

Answer 2

var resultObj = input.reduce((prev, next) => {
    if(prev.hasOwnProperty(next.id)) {
       const currentLatest = prev[next.id];
        // Your logic to check if 'currentLatest' is the latest one or the 'next'
    } else {
        prev[next.id] = next;
    }

    return prev;
}, {});

var result = Object.values(resultObj)

Answer 3

可以将historyno除以-取第二个元素，与之前设置的相同id的值进行比较，如果当前值大于上一个则使用当前值，否则使用当前值最后一个

const input = [{"id": 134116,"user": "admin","historyno": "134116-0"}, {  "id": 134132,  "user": "admin","historyno": "134132-0"}, { "id": 134132,"user": "admin","historyno": "134132-1"}, {  "id": 134133,  "user": "admin",  "historyno": "134133-0"
}, { "id": 134133,"user": "admin","historyno": "134133-1"}];

let final = input.reduce((op,inp)=>{
  op[inp.id] = op[inp.id] || inp
  let lastHisotry = +op[inp.id].historyno.split('-')[1]
  let currentHistory = +inp.historyno.split('-')[1]
  op[inp.id].historyno = currentHistory > lastHisotry ? inp.historyno : op[inp.id].historyno
  return op
},{})
console.log(final);

注意：-如果你的数组已经排序，你不需要这个拆分逻辑，你可以简单地做

const input = [{"id": 134116,"user":"admin","historyno": "134116-0"}, {  "id": 134132,  "user":"admin","historyno": "134132-0"}, { "id": 134132,"user": "admin","historyno": "134132-1"}, {  "id": 134133,  "user": "admin",  "historyno": "134133-0"}, { "id": 134133,"user": "admin","historyno": "134133-1"}];

let final = input.reduce((op,inp) => {
   op[inp.id] = inp
   return op
},{})

console.log(final);

如何创建一个唯一的 json 对象数组并在字段上排序？

How to create a unique array of json objects with sort on a field?

javascript

arrays

ecmascript-6

arrow-functions