I need to create an array of array. It is worth noting that the database is very large and that if any attribute does not have a corresponding value, it sends an empty string. I've tried with map and reduce but I wasn't successful:

Any help will be appreciated.

Below I show an example of the expected output:

outputExpected = [
  ["id", 1, 2],
  ["name", "name1", "name2"],
  ["price", 6.95, 998.95],
  ["promoPrice", 5.91, 333.91],
  ["category", "test1 | test2", "test3 | test4"],
]

Any way to solve this problem performatically?

this is my code:

let arrayObj = [{
    "id": 1,
    "name": "name1",
    "price": 6.95,
    "promoPrice": 5.91,
    "category": ["test1, test2"]
  },
  {
    "id": 2,
    "name": "name2",
    "price": 998.95,
    "promoPrice": 333.91,
    "category": ["test3, test4"]
  }
]

const headers = ["id", "name", "price", "promoPrice", "category"]
const result1 = headers.concat(arrayObj.map((obj) => {
  return headers.reduce((arr, key) => {
    arr.push(obj[key]) return arr;
  }, [])
}))

console.log(result1)

CodePudding user response：

Reduce the array to a Map. On each iteration convert the object to an array of [key, value] pairs using Object.entries(). Use Array.forEach() to iterate the entries and add them to the map. Convert the Map's values iterator to an array using Array.from():

const arr = [{"id":1,"name":"name1","price":6.95,"promoPrice":5.91,"category":["test1", "test2"]},{"id":2,"name":"name2","price":998.95,"promoPrice":333.91,"category":["test3", "test4"]}]

const result = Array.from(arr.reduce((acc, o) => {
  Object.entries(o)
    .forEach(([k, v]) => {
      if(!acc.has(k)) acc.set(k, [k])
      
      acc.get(k).push(Array.isArray(v) ? v.join(' | ') : v)
    })
  
  return acc
}, new Map()).values())

console.log(result)

CodePudding user response：

construct one init array with all possible keys with the wanted order, then uses Array.reduce and Array.forEach to Array.push value for per key based on its index.

const arrayObj = [
  {
  "id":1,
  "name":"name1",
  "price":6.95,
  "promoPrice":5.91,
  "category":["test1", "test2"]
  },
  {
    "id":2,
    "name":"name2",
    "price":998.95,
    "promoPrice":333.91,
    "category":["test3", "test4"]
  }
]

function ConvertToArray2D (items) {
  let init = [['id'], ['name'], ['price'], ['promoPrice'], ['category']]
  if (!items) return init
  return arrayObj.reduce((pre, cur) => {
    init.forEach((key, index) => {
      pre[index].push(Array.isArray(cur[key[0]]) ? cur[key[0]].join('|') : cur[key[0]])
    })
    return pre
  }, init.slice())
}
console.log(ConvertToArray2D(arrayObj))

CodePudding user response：

You could simply map the value and check if an item is an array, then take the joined values or the value itself.

const
    data = [{ id: 1, name: "name1", price: 6.95, promoPrice: 5.91, category: ["test1, test2"] }, { id: 2, name: "name2", price: 998.95, promoPrice: 333.91, category: ["test3, test4"] }],
    headers = ["id", "name", "price", "promoPrice", "category"],
    result = data
        .reduce(
            (r, o) => headers.map((k, i) => [
                ...r[i],
                Array.isArray(o[k]) ? o[k].join(' | ') : o[k]
            ]),
            headers.map(k => [k]),
        );

console.log(result);

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CodePudding user response：

This can be handled with a standard 'zip' after mapping your objects to arrays of values in line with the headers array. (This also allows for the result to be pivoted back)

const zip = (...rs) => [...rs[0]].map((_, c) => rs.map((r) => r[c]));

const headers = ['id', 'name', 'price', 'promoPrice', 'category'];
const arrayObj = [{ id: 1, name: 'name1', price: 6.95, promoPrice: 5.91, category: ['test1', 'test2'] },{ id: 2, name: 'name2', price: 998.95, promoPrice: 333.91, category: ['test3', 'test4'] },];

const result = zip(
  headers,
  ...arrayObj.map((o) => headers.map(h => Array.isArray(o[h]) ? o[h].join(' | ') : o[h]))
);

console.log(result);

// which also allows it to be reversed
console.log(zip(...result));

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