一个数组问题重复值合并问题

Question

const ary = [{    code: 1,    num: 20,}, {    code: 1,    num: 10,}, {    code: 2,    num: 15,}]// 怎样得出下面结果？const ary = [{    code: 1,    num: 30,}, {    code: 2,    num: 15,}]

Answer 1

const ary = [{

  code: 1,

  num: 20

}, {

  code: 1,

  num: 10

}, {

  code: 2,

  num: 15

}]

function merge (list) {

  let result = []

  let cache = {}

  list.forEach(item => {

    let key = item.code

    let index = cache[key]

    if (index !== undefined) {

      result[index].num += item.num

    } else {

      result.push(Object.assign({}, item))

      cache[key] = result.length - 1

    }

  })

  return result

}

merge(list)

Answer 2

function merge(arr) {

  let res = {};

  for(let item of arr) {

    if(res[item.code]) res[item.code].num += item.num;

    else res[item.code] = { code: item.code, num: item.num };  // Avoid modifying the original object.

  }

  return Object.values(res);

}

Answer 3

var abc=[{

        code: 1,

        num: 20,

    }, {

        code: 1,

        num: 10,

    }, {

        code: 2,

        num: 15,

    }]

    var result={};

    for(i=0;i<abc.length;i++){

        if(result[abc[i].code]){

            result[abc[i].code]+=abc[i].num;

        }else{

            result[abc[i].code]=abc[i].num;

        }

    }

    var keyvalue=[];

    for(var key in result){

        keyvalue.push({code:key,num:result[key]})

    }

    console.log(keyvalue)

Answer 4

new Set(arr)