JSFiddle - React, Tailwind, and code Playground

by Vladymyr Shevchuk

JavaScript

const arr = [
  {
  "id": "bytovaya-texnika",
  "title": "Бытовая техника",
  "count": 52,
  "weight": 1,
  "subcategories": [{
    "id": "tovary-dlya-kuxni",
    "title": "Товары для кухни",
    "count": 15,
    "category": "bytovaya-texnika",
    "weight": 2
  }, {
    "id": "tovary-dlya-doma",
    "title": "Товары для дома",
    "count": 16,
    "category": "bytovaya-texnika",
    "weight": 121
  }, {
    "id": "krasota-i-zdorove",
    "title": "Красота и здоровье",
    "count": 21,
    "category": "bytovaya-texnika",
    "weight": 208
  }]
}, 
  {
  "id": "smartfony-planshety-i-fototexnika",
  "title": "Смартфоны",
  "count": 51,
  "weight": 276,
  "subcategories": [{
    "id": "smartfony-i-gadzhety",
    "title": "Смартфоны и гаджеты",
    "count": 22,
    "category": "smartfony-planshety-i-fototexnika",
    "weight": 277
  }, {
    "id": "fototexnika",
    "title": "Фототехника",
    "count": 21,
    "category": "smartfony-planshety-i-fototexnika",
    "weight": 299
  }, {
    "id": "planshety-elektronnye-knigi",
    "title": "Планшеты, электронные книги",
    "count": 8,
    "category": "smartfony-planshety-i-fototexnika",
    "weight": 362
  }]
}
];

const result = arr.map(item => {
  return item.subcategories.map(category => {
    return `${item.title} > ${category.title}`;
  });
});

console.log(result.flat());