Convert flat array of array into nested objects

Question

I have an array of values and I want to convert them into nested objects if the category i.e 1st element exists then the next subcategories are pushed in this. Can we achieve this, I am beginner please help

for example:

    const newCat = [
                     [
                        "Grocery", // category
                        "Food & Drink", // sub-category
                        "Snacks, Crisps and Sweets", // sub-sub-category
                    ],
                    [
                        "Grocery",
                        "Canned, Dry & Packaged Food",
                        "Pickled Foods",
                    ],
                    [
                        "Grocery",
                        "Food & Drink",
                    ],
                    [
                        "Grocery",
                        "Food & Drink",
                        "Nuts, Dates & Dried Fruits",
                    ],
                    [
                        "Grocery",
                        "World Specialities",
                        "India",
                    ],

                  ]

OUTPUT -
[
    {
    CategoryName: "Grocery",
    SubCategories: [
      {
        CategoryName: "Food & Drink",
        SubCategories: [
          {
            CategoryName: "Snacks, Crisps, and Sweets",
          },
        ],
      },
      {
        CategoryName: "Canned, Dry & Packaged Food",
        SubCategories: [
          {
            CategoryName: "Pickled Foods",
          },

        ],

      },
    ],
  }
]

BigLiao · Accepted Answer · 2022-07-19 12:56:08Z

function flatArray(arr) {
  const result = [];
  for (let item of arr) {
    const [c1, c2, c3] = item;
    const findC1 = result.find(c => c.categoryName === c1);
    if (findC1) {
      if (!c2) {
        continue;
      }
      const findC2 = findC1.subCategorys.find(c => c.categoryName === c2);
      if (findC2) {
        if (!c3) {
          continue;
        }
        findC2.subCategorys.push(c3);
      } else {
        findC1.subCategorys.push({
          categoryName: c2,
          subCategorys: [c3]
        });
      }
    } else {
      result.push({
        categoryName: c1,
        subCategorys: [
          {
            categoryName: c2,
            subCategorys: [c3]
          }
        ]
      })
    }
  }  
  
  return result;
}


// Test case
const newCat = [
   [
      "Grocery", // category
      "Food & Drink", // sub-category
      "Snacks, Crisps and Sweets", // sub-sub-category
  ],
  [
      "Grocery",
      "Canned, Dry & Packaged Food",
      "Pickled Foods",
  ],
  [
      "Grocery",
      "Food & Drink",
  ],
  [
      "Grocery",
      "Food & Drink",
      "Nuts, Dates & Dried Fruits",
  ],
  [
      "Grocery",
      "World Specialities",
      "India",
  ],

];

console.log(flatArray(newCat));

TymoteuszLao · Accepted Answer · 2022-07-19 19:58:18Z

1

const newCat = [
  [
    "Grocery", // category
    "Food & Drink", // sub-category
    "Snacks, Crisps and Sweets", // sub-sub-category
  ],
  [
    "Grocery",
    "Canned, Dry & Packaged Food",
    "Pickled Foods",
  ],
  [
    "Grocery",
    "Food & Drink",
  ],
  [
    "Grocery",
    "Food & Drink",
    "Nuts, Dates & Dried Fruits",
  ],
  [
    "Grocery",
    "World Specialities",
    "India",
  ],
  ["Electronics", "Speakers", "Bluetooth Speakers", "JBL", ],
]

const output = []

newCat.forEach((e) => {
  let indexofCategory = output.findIndex((category) => category.CategoryName === e[0]);
  if (indexofCategory === -1) {
    output.push({
      CategoryName: e[0],
      SubCategories: []
    })
    indexofCategory = output.length - 1;
  }
  if (e[1]) {
    let indexofSubcategory = output[indexofCategory].SubCategories.findIndex((category) => category.CategoryName === e[1]);
    if (indexofSubcategory === -1) {
      output[indexofCategory].SubCategories.push({
        CategoryName: e[1],
        SubCategories: []
      })
      indexofSubcategory = output[indexofCategory].SubCategories.length - 1;
    }
    if (e[2]) {
      let indexofSubSubcategory = output[indexofCategory].SubCategories[indexofSubcategory].SubCategories.findIndex((category) => category.CategoryName === e[2]);
      if (indexofSubSubcategory === -1) {
        output[indexofCategory].SubCategories[indexofSubcategory].SubCategories.push({
          CategoryName: e[2],
          SubCategories: [],
        })
        indexofSubSubcategory = output[indexofCategory].SubCategories[indexofSubcategory].SubCategories.length - 1;
      }
      if (e[3]) {
        const indexofSubSubSubcategory = output[indexofCategory].SubCategories[indexofSubcategory].SubCategories[indexofSubSubcategory].SubCategories.findIndex((category) => category.CategoryName === e[3]);
        if (indexofSubSubSubcategory === -1) output[indexofCategory].SubCategories[indexofSubcategory].SubCategories[indexofSubSubcategory].SubCategories.push({
          CategoryName: e[3]
        })
      }
    }
  }
});

console.log(output)

edited Jul 19, 2022 at 19:58

answered Jul 19, 2022 at 13:08

TymoteuszLao

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2 Comments

Ravi Vishwakarma Over a year ago

just one problem here I am facing that there can be 4th level also like [ "Electronics", "Speakers", "Bluetooth Speakers", "JBL", ], can you please let me know how to do this

TymoteuszLao Over a year ago

@RaviVishwakarma I updated my code. The overall rule is very simple - for every level, you should add another part of code where you check if a specific item at a specific level exists and if it does not exists add it. Although I believe it can be done more 'abstract' and there is a lot of room for improvement.

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