根据索引数组设置数组

Question

I want to set a boolean value in a nested object structure, based on a list of indexes

The data I want to update looks like this:

let categories = [{
    "name": "Cat 1",
    "subs": [{
        "name": "Sub Cat 1.1",
        "subs": [],
        "checked": false
      },
      {
        "name": "Sub Cat 1.2",
        "subs": [],
        "checked": false
      }
    ],
    "checked": false
  },
  {
    "name": "Cat 2",
    "subs": [],
    "checked": false
  }
];

The indexes are stored in an array:

let categoryIndexs = [0,1]

So based on categoryIndexs I want to change the checked property of the object with name "Sub Cat 1.2" to true .

It is like transforming the array [0,1] to find categories[0].subs[1] and update its checked property.

So far I managed to get the value and edit it separately, but how to change the categories variable directly?

  let categoryIndexs = [0,1]

  let tmp_array = categories;

  for(var i = 0; i < categoryIndexs.length;i++){
      if(i == 0){
        tmp_array = tmp_array[categoryIndexs[i]]
      } else {
        tmp_array = tmp_array.subs[categoryIndexs[i]]
      }
  }

  tmp_array.checked = true
  console.log(tmp_array)

The solution needs to be dynamic, so that if "Sub Cat 1.2" would have a nested entry in its own subs array, I can access it using categoryIndexs like [0,1,0]

Answer 1

You can iterate the given indexes in a loop and at the same time go deeper in your data structure, like in this function:

 function setChecked(categories, categoryIndexes) { let obj = null; for (let index of categoryIndexes) { obj = categories[index]; categories = obj.subs; } obj.checked = true; } let categories = [{"name": "Cat 1","subs": [{"name": "Sub Cat 1.1","subs": [],"checked": false},{"name": "Sub Cat 1.2","subs": [],"checked": false}],"checked": false},{"name": "Cat 2","subs": [],"checked": false}]; setChecked(categories, [0,1]); console.log(categories);

Answer 2

You could use reduce to get the last subs up until the last subs and update the checked property

 let categories = [{"name": "Cat 1","subs": [{"name": "Sub Cat 1.1","subs": [],"checked": false},{"name": "Sub Cat 1.2","subs": [],"checked": false}],"checked": false},{"name": "Cat 2","subs": [],"checked": false}]; let categoryIndexs = [0, 1]; function update(categories, indices) { const last = indices.pop(); // remove the last const redued = indices.reduce((acc, i) => acc[i].subs, categories); redued[last].checked = true; return categories } console.log(update(categories, categoryIndexs))

Answer 3

You could reduce the array by looking to the index of the iteration and take either subs or the item.

 const getValue = (subs, indices) => indices.reduce( ({ subs }, i) => subs[i], { subs } ); let categories = [{ name: "Cat 1", subs: [{ name: "Sub Cat 1.1", subs: [], checked: false }, { name: "Sub Cat 1.2", subs: [], checked: false }], checked: false }, { name: "Cat 2", subs: [], checked: false }], indices = [0, 1]; console.log(getValue(categories, indices, 'subs'));