Find empty arrays in nested array and remove them in Javascript

Question

I have a nested and hierarchical array of objects, which looks like this

[{
"id": 0,
"name": "E00-E90 Stoffwechselstörungen",
"parentId": null,
"children": [{
    "id": 1,
    "name": "E70-E90 Stoffwechselstörungen",
    "parentId": 0,
    "children": [{
        "id": 2,
        "name": "E70.- Störungen des Stoffwechsels aromatischer Aminosäuren",
        "parentId": 1,
        "children": []
    }, {
        "id": 3,
        "name": "E71.- Störungen des Stoffwechsels verzweigter Aminosäuren und des Fettsäurestoffwechsels",
        "parentId": 1,
        "children": []
    }, {
        "id": 4,
        "name": "E72.- Sonstige Störungen des Aminosäurestoffwechsels",
        "parentId": 1,
        "children": []
    },
    ...

Now I want to remove the empty array "children": [] from the last children.

I've tried it with reduce but it doesn't work without any error.

   var lastElementLength = list.length - 1

   const findItemNested = (arr, itemId, nestingKey) => (
        arr.reduce((a, item) => {
          if (a) return a;
          if (item.id === itemId) return item;
          if (item[nestingKey]) return findItemNested(item[nestingKey], itemId, nestingKey)
        }, null)
    );

    const resEmptyChildren = findItemNested(roots, lastElementLength, "children");
    
    console.log('resEmptyChildren', resEmptyChildren)

Answer 1

You could use recursion for that.

 var tInput = [{ "id": 0, "name": "E00-E90 Stoffwechselstörungen", "parentId": null, "children": [{ "id": 1, "name": "E70-E90 Stoffwechselstörungen", "parentId": 0, "children": [{ "id": 2, "name": "E70.- Störungen des Stoffwechsels aromatischer Aminosäuren", "parentId": 1, "children": [] }, { "id": 3, "name": "E71.- Störungen des Stoffwechsels verzweigter Aminosäuren und des Fettsäurestoffwechsels", "parentId": 1, "children": [] }, { "id": 4, "name": "E72.- Sonstige Störungen des Aminosäurestoffwechsels", "parentId": 1, "children": [] }] }] }]; (function removeEmptyChildrenProperties(input){ console.log('Checking id:', input.id); if(input.hasOwnProperty('children')){ if(input.children && input.children.length){ input.children.forEach(removeEmptyChildrenProperties) } else{ console.log('Remove children on id:', input.id); delete input.children } }; return input }).apply(null, tInput); console.log(JSON.stringify(tInput));