Dealing with looping through nested arrays

Question

I have data array, which has nested arrays inside (level1arr, leve21arr ...)

const data = [
  {
    level1arr: [
      {
        level2arr: [{ id: 1, isValid: true }, { id: 2, isValid: true }, { id: 3, isValid: true }],
      },
      {
        level2arr: [{ id: 4, isValid: true }, { id: 5, isValid: true }, { id: 6, isValid: true }],
      },
    ],
  },
  {
    level1arr: [
      {
        level2arr: [{ id: 7, isValid: true }, { id: 8, isValid: true }, { id: 9, isValid: true }],
      },
      {
        level2arr: [{ id: 10, isValid: true }, { id: 11, isValid: true }, { id: 12, isValid: true }],
      },
    ],
  },
];

I also have another array:

const invalidIds = [2,5]

I want to find elements with apecyfic id and change isValid property to false. Is it better way than iteratinf over multiple nested arrays, like that:

data.forEach(lvl1 => {
  lvl1.level1arr.forEach(lvl2 => {
    lvl2.level2arr.forEach(element => {
      // further nesting
    });
  });
})

Such iterating over multiple arrays is not good for performance. What is the best way to handle such case with nested arrays?

If you need to do many lookups, the best thing to do would be to transform the data structure into something more appropriate. — Pointy, Oct 14 '21 at 14:26

score 0 · Answer 1 · answered Oct 14 '21 at 14:17

If it were nested arrays, you could use Array.prototype.flat(). However, you have a mix of nested objects and arrays. You will have to write a custom "flattener" for this data structure. Check this answer for details: how to convert this nested object into a flat object?

score 0 · Answer 2 · answered Oct 14 '21 at 17:17

You can use recursion until you reach the level you need. Here's one way to do it.

const data = [{
    level1arr: [{
        level2arr: [{
          id: 1,
          isValid: true
        }, {
          id: 2,
          isValid: true
        }, {
          id: 3,
          isValid: true
        }],
      },
      {
        level2arr: [{
          id: 4,
          isValid: true
        }, {
          id: 5,
          isValid: true
        }, {
          id: 6,
          isValid: true
        }],
      },
    ],
  },
  {
    level1arr: [{
        level2arr: [{
          id: 7,
          isValid: true
        }, {
          id: 8,
          isValid: true
        }, {
          id: 9,
          isValid: true
        }],
      },
      {
        level2arr: [{
          id: 10,
          isValid: true
        }, {
          id: 11,
          isValid: true
        }, {
          id: 12,
          isValid: true
        }],
      },
    ],
  },
];

const invalidIds =[2,5]

const findId = (object, key, value) => {
  if (Array.isArray(object)) {
    for (const obj of object) {
      findId(obj, key, value);
    }
  } else {
    if (object.hasOwnProperty(key) && object[key] === value) {
      object.isValid = false;
      return object
    }
    for (const k of Object.keys(object)) {
      if (typeof object[k] === "object") {
        findId(object[k], key, value);
      }
    }
  }
}

invalidIds.forEach(id => findId(data, "id", id))
console.log(data)

Dealing with looping through nested arrays

2 Answers2