javascript - How does one, within a nested object structure, recursively collect different types of object ids?

Question

I have this data :

{
   "id": 26578,
   "label": "CatA",
   "value": 26578,
   "children": [
     {
        "id": 26579,
        "label": "CatB",
        "value": 26579,
        "children": [
           {
              "id": 26580,
              "label": "CatC",
              "value": 26580,
              "children": null
           },
           {
              "id": 26581,
              "label": "CatD",
              "value": 26581,
              "children": null
           }
        ]
     }
   ]
},

I know the value 26578, I called chosenSubcategoryId

I want to get 2 arrays :

expanded = [26578, 26579]
checked  = [26580, 26581]

I try like this :

const recursion = (item, chosenSubcategoryId) => {
        if (Array.isArray(item)) {
            item.map(item => {
                if (item.id === chosenSubcategoryId) {
                    recursion(item.children, item.id);
                }
            })
        }
}
recursion(this.props.chosenCategory.children, this.props.chosenSubcategory.id);

But not working properly. Please help me ! Thx in advance.

question from:https://stackoverflow.com/questions/65845465/how-does-one-within-a-nested-object-structure-recursively-collect-different-ty

Answer 1

After you've found the subcategory this condition item.id === chosenSubcategoryId would always be false.

To get the ids of the subcategory items, use an internal recursion. I've used Array.forEach() to iterate the items, add the ids to the respective arrays in the result (res), and iterate the children recursively.

const fn = o => {
  const res = { expanded: [], checked: []};
  
  const recursion = o => {
    if(o.children === null) {
      res.checked.push(o.id);
    } else {
      res.expanded.push(o.id);
      
      o.children.forEach(recursion);
    }
  }
  
  recursion(o);
  
  return res;
};

const obj = {"id":26578,"label":"CatA","value":26578,"children":[{"id":26579,"label":"CatB","value":26579,"children":[{"id":26580,"label":"CatC","value":26580,"children":null},{"id":26581,"label":"CatD","value":26581,"children":null}]}]};

const result = fn(obj);

console.log(result);