Searching in nested arrays for empty object in JavaScript

Question

var array = [
  {
    key: 'value',
    subArray: [{ key: 'value', subArray: [{}] }]
  },
  {
    key: 'value',
    subArray: [{ key: 'value', subArray: [{ key: 'value', subArray: [] }] }]
  },
  { key: 'value', subArray: [] }
];

In my application I've got array of objects. Each objects have field containing another array which can contain another object with field containing array and so on. In some cases objects could be empty. I need write function which will be iterate over all arrays, finds emty objects and remove them. How can I achive this?

You can use DFS algorithm here. geeksforgeeks.org/depth-first-search-or-dfs-for-a-graph — Harun Or Rashid
– Harun Or Rashid, Commented Jul 16, 2018 at 11:14
In fact, I'm trying to build some form builder. In application user cad add some inputs. Each inputs can have subInputs. This varriable that I show above is containing current state of builded form. Empty subArray means that inputs has no subInputs. If subArray contains empty Object that means that inputs had subInputs but subInputs was deleted. — P.Mol
– P.Mol, Commented Jul 16, 2018 at 11:40

Joven28 · Accepted Answer · 2018-07-16 11:43:12Z

1

I think the solution is to use recursion.

var array = [
  {
    key: 'value',
    subArray: [{ key: 'value', subArray: [{}] }]
  },
  {
    key: 'value',
    subArray: [{ key: 'value', subArray: [{ key: 'value', subArray: [] }] }]
  },
  { key: 'value', subArray: [] }
];


function lookup(subArr) {
    subArr.forEach((sa, i) => {
        if (Object.keys(sa).length == 0) {
           delete subArr[i];
        } else {
           lookup(sa.subArray);
        }
    });
}


array.forEach(a => {
    lookup(a.subArray);
});


console.log(array);

edited Jul 16, 2018 at 11:43

answered Jul 16, 2018 at 11:31

Joven28

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Comments

Jim Wright · Accepted Answer · 2018-07-16 11:22:41Z

0

try this

for (var i = 0; i < array.length; i++ ) {
  if (array[i].subArray.length != 0) {
    if (Object.keys(array[i].subArray).length)) {
      delete Object.keys(array[i].subArray
    }
  }
}

may be useful for you

edited Jul 16, 2018 at 11:22

Jim Wright

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answered Jul 16, 2018 at 11:16

Soumya Gangamwar

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1 Comment

Jim Wright Over a year ago

This isn't recursive so will only work for a certain depth, also it seems you are deleting arrays that have length which is the opposite of what OP is trying to do.

Harun Or Rashid · Accepted Answer · 2018-07-16 11:55:05Z

0

Try like this. Hope it will help to figure out the solution :

for (var i = 0; i < array.length; i++ ){
    if(array[i].subArray)
    {
        removeEmptyItems(array[i].subArray);
    } 
}

removeEmptyItems(item: any) {
    if(item.length == 0){
        delete item;
        return;
    }
    if (item.subArray) {            
        removeEmptyItems(item.subArray);
    } 
}

edited Jul 16, 2018 at 11:55

answered Jul 16, 2018 at 11:30

Harun Or Rashid

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2 Comments

P.Mol Over a year ago

When You are calling removeEmptyItems You are give it subArray as argument. Thats ok. But then You are checking if its length is equal 0 thats means You are checking if subArray is empty and then if is delete subArr. Thats not what i woudl like to achive. I need check if subArray contains empty object. SubArray can contains infinitive number of objects. I need detect if some of this objects are empty: {} and then a need delete only this empty objects from array, not whole array.

Harun Or Rashid Over a year ago

Well, i just wanted to share my idea. You need to modify this :)

Leonid Pyrlia · Accepted Answer · 2018-07-16 12:39:47Z

If you want to find empty objects and remove them (in other words, turn subArray: [{}] to subArray: []), then you can do it with recursive function that replaces all occurrences of arrays with one empty object with an empty arrays:

var array = [
  {
    key: 'value',
    subArray: [{ key: 'value', subArray: [{}] }]
  },
  {
    key: 'value',
    subArray: [{ key: 'value', subArray: [{ key: 'value', subArray: [] }] }]
  },
  { key: 'value', subArray: [] }
];

function removeEmptyObjects(obj) {

    var objCopy = Object.assign({}, obj);

    Object.keys(objCopy).forEach(key => {

        if (!Array.isArray(objCopy[key])) return;

        var containsEmptyObject = objCopy[key].length === 1 && typeof objCopy[key][0] === 'object' && Object.keys(objCopy[key][0]).length === 0;

        objCopy[key] = containsEmptyObject ? [] : objCopy[key].map(removeEmptyObjects);

    });

    return objCopy;

}

var result = array.map(removeEmptyObjects);

console.log(JSON.stringify(result, null, 2));

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