Find all possible fields and their types from a MongoDB collection

findschema.js

var obj = {};

function reduce(accum, doc) {
    for (var key in doc) {
        if (doc.hasOwnProperty(key) && typeof doc[key] !== 'function') {
            const type = typeof doc[key]
            if (type === 'object') {
                const aKey = (accum[key] && typeof accum[key] === 'string') ? key + '_obj' : key
                accum[aKey] = accum[aKey] ? accum[aKey] : {}
                reduce(accum[aKey], doc[key])
            } else {
                if (!accum[key]) {
                    accum[key] = type
                } else if (typeof accum[key] === 'string' && accum[key].indexOf(type) === -1) {
                    accum[key] = obj[key] + ',' + type
                }
            }
        }
    }
}

db.myCollection.find({}).limit(100000).forEach(doc => reduce(obj, doc));
obj;

result.json

[
  {
    "_id": {
    },
    "Account": "string",
    "Amount": "string",
    "Destination": "string",
    "Fee": "string",
    "Flags": "number",
    "TransactionType": "string",
    "amount": "string,number",
    "amount_obj": {
      "value": "number"
    },
    "attachment": {
    },
    "balance": "string",
    "balance_obj": {
      "value": "number",
      "USD": "number",
      "EURO": {
        "value": "number"
      }
    },
    "brokerFees": {
      "0": {
        "value": "number"
      },
      "1": "number",
      "1_obj": {
        "value": "number"
      }
    },
    "confirmations": "number,string",
    "date": {
      "value": "number"
    },
    "details": {
      "address": "string",
      "amount": "number",
      "category": "string",
      "amount_obj": {
        "value": "number"
      }
    },
    "fee": "number",
    "fee_obj": {
      "value": "number",
      "amount": {
        "value": "number"
      },
      "asset_id": {
        "value": "number"
      }
    },
    "ledger_entries": {
      "0": {
        "from_account": "string",
        "to_account": "string",
        "amount": {
          "amount": {
            "value": "number"
          },
          "asset": "number"
        },
        "memo": "string",
        "running_balances": {
          "0": {
            "0": "string",
            "1": {
              "0": {
                "0": {
                  "value": "number"
                },
                "1": {
                  "amount": {
                    "value": "number"
                  },
                  "asset": {
                    "value": "number"
                  }
                }
              },
              "1": {
                "0": {
                  "value": "number"
                },
                "1": {
                  "amount": {
                    "value": "number"
                  },
                  "asset_id": {
                    "value": "number"
                  }
                }
              }
            }
          }
        }
      }
    },
    "pending": {
      "_id": {},
      "withdrawalAmount": "string",
      "status": "string",
      "uuid": "string"
    },
    "result": "string",
    "result_obj": {
      "0": {
        "amount": "string",
        "date": "string",
        "rate": "string",
        "total": "string",
        "tradeID": "string",
        "type": "string"
      },
      "1": {
        "amount": "string",
        "date": "string",
        "rate": "string",
        "total": "string",
        "tradeID": "string",
        "type": "string"
      }
    }
  }
]