Javascript - remove element from an array if the id in parent of an element is also in the array-CodePudding

I have an array that has parent-child values. I need to remove the elements from the array if its parent is already there in the array.

Sample data:

const data = [
  {
    id: "1",
    parentIds: []
  },
  {
    id: "2",
    parentIds: []
  },
  {
    id: "3",
    parentIds: ["1"]
  },
  {
    id: "4",
    parentIds: ["1", "3"]
  },
  {
    id: "5",
    parentIds: ["6"]
  }
]

The expected output is:

[
  {
    id: "1",
    parentIds: []
  },
  {
    id: "2",
    parentIds: []
  },
  {
    id: "5",
    parentIds: ["6"]
  }
]

I tried with the following code:

for (let i = selectedItems.length - 1; i >= 0; i--) {
      for (let j = selectedItems.length - 1; j >= 0; j--) {
        if (selectedItems[j].parentsIds.includes(selectedItems[i].id)) {
          selectedItems.splice(i, 1)
        }
      }
    }

But this fails with Cannot read properties of undefined (reading 'id') after splicing first match.

It there anyway this can be achieved?

CodePudding user response：

First get an array of all id's using map().

Then use filter() to remove those where some() does not includes() in allIds

let data = [{id: "1", parentIds: [] }, {id: "2", parentIds: [] }, {id: "3", parentIds: ["1"] }, {id: "4", parentIds: ["1", "3"] }, {id: "5", parentIds: ["6"] } ];

const allIds = data.map(d => d.id);

data = data.filter((d, x) => !d.parentIds.some(a => allIds.includes(a)));

console.log(data);

CodePudding user response：

You need to .filter your data, to remove all items where .some of the parentIds are found in your data:

const data = [
  { id: "1", parentIds: [] },
  { id: "2", parentIds: [] },
  { id: "3", parentIds: ["1"] },
  { id: "4", parentIds: ["1", "3"] },
  { id: "5", parentIds: ["6"] }
];

const result = data.filter(
  row => !row.parentIds.some(
    id => data.some(d => d.id === id)
  )
);
      
console.log(result);

CodePudding user response：

First extract an array of ids in the original array:

const ids = data.map(el => el.id)

Then filter the original array intersecting each element's parents array with the extracted ids array:

data.filter(el => el.parentIds.filter(parentId => ids.includes(parentId)).length === 0);

See this question Simplest code for array intersection in javascript for an explanation of how array intersection works.