Filter an array of object to remove the duplicates and get some properties for that duplicate object-CodePudding

pls help me out to solve this below problem.

the below one is the main array

let arr1 = [
   {grId: 2, grTitle: "cls 1", secTitle: "sec A"},
   {grId: 2, grTitle: "cls 1", secTitle: "sec B"},
   {grId: 3, grTitle: "cls 2", secTitle: "sec A"},
   {grId: 3, grTitle: "cls 2", secTitle: "sec B"},
 ]

I want filter like below array of object

let newArr = [
   {id: 2, title: "cls 1", secList: [{secTitle: "sec A"}, {secTitle: "sec B"}]}
   {id: 3, title: "cls 2", secList: [{secTitle: "sec A"}, {secTitle: "sec B"}]}
 ]

CodePudding user response：

Using Lodash:

let arr1 = [
  {grId: 2, grTitle: "cls 1", secTitle: "sec A"},
  {grId: 2, grTitle: "cls 1", secTitle: "sec B"},
  {grId: 3, grTitle: "cls 2", secTitle: "sec A"},
  {grId: 3, grTitle: "cls 2", secTitle: "sec B"},
]

console.log(
  _.values(
    _.map(
      _.groupBy(arr1, "grId"),
      (values) => ({
        id: values[0].grId,
        title: values[0].grTitle,
        secList: _.map(values, ({ secTitle }) => ({ secTitle })),
      })
    )
  )
)

<script src="https://unpkg.com/lodash"></script>

CodePudding user response：

the previous post was suggesting to use reduce in my opinion reduce is much harder to read so I chose to use loops instead, but feel free to change it to your liking.

let arr1 = [
   {grId: 2, grTitle: "cls 1", secTitle: "sec A"},
   {grId: 2, grTitle: "cls 1", secTitle: "sec B"},
   {grId: 3, grTitle: "cls 2", secTitle: "sec A"},
   {grId: 3, grTitle: "cls 2", secTitle: "sec B"},
 ]

let lookupTable = {};

for (const item of arr1) {
  if (item.grId in lookupTable) {
    lookupTable[item.grId].secList.push({secTitle: item.secTitle });
  } else {
    lookupTable[item.grId] = {title: item.grTitle, secList: [{ secTitle: item.secTitle }] };
  }
}

let newArr = [];
for (const [id, item] of Object.entries(lookupTable)) {
  newArr.push({id, title: item.title, secList: item.secList });
}

console.log(newArr);

/*
let newArr = [
   {id: 2, title: "cls 1", secList: [{secTitle: "sec A"}, {secTitle: "sec B"}]}
   {id: 3, title: "cls 2", secList: [{secTitle: "sec A"}, {secTitle: "sec B"}]}
 ]*/