Question 318907 in Javascript Question posted in
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JavaScript filter array with other nested array using key

Hi stuck at one point I have two set of arrays (topicsList & hierarchyList)

let topicsList = [{
    "topicId": 1,
    "topicName": "Introduction",
  },
  {
    "topicId": 2,
    "topicName": "How to Guide",
  },
  {
    "topicId": 3,
    "topicName": "Support",
  },
  {
    "topicId": 6,
    "topicName": "Lamborghini",
  },
  {
    "topicId": 7,
    "topicName": "Mercedes Benz",
  },
  {
    "topicId": 10,
    "topicName": "Skoda",
  }
]

let hierarchyList = [{
    "topicId": 1,
    "topicName": "Introduction",
  },
  {
    "topicId": 2,
    "topicName": "How to Guide",
    "children": [{
      "topicId": 6,
      "topicName": "Lamborghini",
      "children": [{
        "topicId": 10,
        "topicName": "Skoda",
      }]
    }]
  },
  {
    "topicId": 3,
    "topicName": "Support"
  }
]

topicIds = new Set(hierarchyList.map(({ topicId }) => topicId));

topicsList = topicsList.filter(({ topicId }) => !topicIds.has(topicId));

console.log(topicsList);

I am filtering out the TopicsList based on the topicId present in hierarchyList, but hierarchyList now also has this nested childrens and it can be n levels deep

I also need to check now if this topicId is also present in nested childrens array if it does I need to do the same filter it out from Topic List. I’m not sure how can i achieve this behaviour

Expected O/P

TopicList = [{
  "topicId": 7,
  "topicName": "Mercedes Benz",
}]
Tags:

2

Answers


  1. 0

    just use a set and then map with this simple function which you then filter

    function filterTopics(topicsList, hierarchyList) {
  const topicIds = new Set(hierarchyList.map(({ topicId }) => topicId));

  return topicsList.filter(({ topicId }) => {
    if (topicIds.has(topicId)) {
      // Check if the topicId is present in the nested children
      const hasNestedChild = hierarchyList.some(({ children }) =>
        children ? filterTopics([{ topicId }], children).length > 0 : false
      );

      return !hasNestedChild;
    }
    return true;
  });
}

// call it here
const filteredTopicsList = filterTopics(topicsList, hierarchyList);
console.log(filteredTopicsList);
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  2. 0

    You can use .flatMap() on your hierarchyList. For each object, you can extract its topicId like you do currently, but also its children array (defaulting it to an empty array if it doesn’t exist via destructuring). You can then recursively call .flatMap() on the children, spreading the results of the recursive calls into the mapped array. Once you’ve built the array of ids, you can pass it to your Set for quick lookup and deduplication as you do currently:

    let topicsList = [{ "topicId": 1, "topicName": "Introduction", }, { "topicId": 2, "topicName": "How to Guide", }, { "topicId": 3, "topicName": "Support", }, { "topicId": 6, "topicName": "Lamborghini", }, { "topicId": 7, "topicName": "Mercedes Benz", }, { "topicId": 10, "topicName": "Skoda", } ];
let hierarchyList = [{ "topicId": 1, "topicName": "Introduction", }, { "topicId": 2, "topicName": "How to Guide", "children": [{ "topicId": 6, "topicName": "Lamborghini", "children": [{ "topicId": 10, "topicName": "Skoda", }] }] }, { "topicId": 3, "topicName": "Support" } ];

const mapHeirarchy = list => list.flatMap(({ topicId, children = [] }) => [topicId, ...mapHeirarchy(children)]);

const topicIds = new Set(mapHeirarchy(hierarchyList));
topicsList = topicsList.filter(({ topicId }) => !topicIds.has(topicId));

console.log(topicsList);
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