Print the shape of input with used values

index.js

const printValues = (data) => {
    const getType = (value) => {
        if (Array.isArray(value)) return 'array';
        if (null === value) return 'null';
        return typeof value;
    };
    const initResult = () => ({ _type: new Set([]), _values: new Set() })

    const updateValues = (result = initResult(), item) => {
        const type = getType(item);
        result._type.add(type);
        if (type === 'object') {
            Object.keys(item).forEach((key) => (result[key] = updateValues(result[key], item[key])));
        } else if (type === 'array') {
            return item.reduce(updateValues, result)
        } else {
            result._values.add(item);
        }

        return result;
    };

    return updateValues(initResult(), data);
};

const simplifyOutput = (output) => {
    const simplified = {};
    for (const key in output) {
        if (output[key]._type) {
            simplified[key] = [...output[key]._type];
        }
    }
    return simplified;
};

const convertToArrays = (output, maxValuesLength = -1, converted = {}) => {
  if (output._type) {
    converted._type = [...output._type];
    converted._values = [...output._values].filter((_, i) => i % Math.ceil(output._values.size / maxValuesLength) === 0);
  }
  for (const key in output) {
    if (['_type', '_values'].includes(key)) {
      continue;
    }
    converted[key] = convertToArrays(output[key], maxValuesLength, converted[key])
  }
  return converted;
};

printValues([
    {"a": "string"}, 
    {"array": [1, 2, 3]},
    {"obj": [{"1": 1}, {"1": 2}]},
])
/*
{
  a: {
    _type: new Set(['string']),
    _values: new Set(['string'])
  },
  array: {
    _type: new Set(['array', 'number']),
    _values: new Set([1, 2, 3])
  },
  obj: {
    1: {
      _type: new Set(['number']),
      _values: new Set([1, 2])
    },
    _type: new Set(['array', 'object']),
    _values: new Set()  // empty set
  }
}

*/

simplifyOutput(printValues([
    {"a": "string"}, 
    {"array": [1, 2, 3]},
    {"obj": [{"1": 1}, {"1": 2}]},
]))
/*
{
  "a": [
    "string"
  ],
  "array": [
    "array",
    "number"
  ],
  "obj": [
    "array",
    "object"
  ]
}
*/

convertToArrays(printValues([
    {"a": "string"}, 
    {"array": [1, 2, 3]},
    {"obj": [{"1": 1}, {"1": 2}]},
]))
/*
{
  "_type": [
    "array",
    "object"
  ],
  "_values": [],
  "a": {
    "_type": [
      "string"
    ],
    "_values": [
      "string"
    ]
  },
  "array": {
    "_type": [
      "array",
      "number"
    ],
    "_values": [
      1
    ]
  },
  "obj": {
    "1": {
      "_type": [
        "number"
      ],
      "_values": [
        1
      ]
    },
    "_type": [
      "array",
      "object"
    ],
    "_values": []
  }
}
*/