javascript 多维数组合并的问题？

Question

            var arr = [{
                id: 1,
                name: 'a'
            }, {
                id: 1,
                name: 'b'
            }, {
                id: 2,
                name: 'c'
            }, {
                id: 2,
                name: 'd'
            }];

实现结果：

arr = [{
                id: 1,
                name: ['a', 'b']
            }, {
                id: 2,
                name: ['c', 'd']
            }];

请问 怎么实现？

Answer 1

let newArr = []
arr.forEach(el=>{
    const result = newArr.findIndex(ol=>{return el.id === ol.id})
    if(result!== -1){
        newArr[result].name.push(el.name)
    }else{
        newArr.push({id:el.id,name:[el.name]})
    } 
})
console.log(newArr)

Answer 2

let t = {}
arr.forEach(val => {
  t[val.id] = t[val.id] || { name: [] }
  t[val.id].name.push(val.name)
})
let res = []
for (let val of Object.keys(t)) {
  res.push({
    id: val,
    name: t[val].name
  })
}
console.log(res)

Answer 3

function mergeArr(arr) {
  const flatObj = arr.reduce((iter , val) => {
    if(iter[val.id]) {
      iter[val.id].name.push(val.name)
    } else {
      iter[val.id] = {
        id: val.id,
        name: [val.name]
      }
    }
    return iter
  }, {})
  const mergeRst = Object.keys(flatObj).map(v => flatObj[v])
  return mergeRst
}
mergeArr(arr)

Answer 4

我这个一句话的阅读性差了点，供参考：
arr.reduce((m,c)=>[m.find(x=>x.id===c.id).name.push(c.name), m][1], Array.from(new Set(arr.map(n=>n.id)), m=>new Object({id:m,name:[]})));