How to bring form data to a certain form?

Question

JavaScript

I have a specific JSON that I use to build a form:

{
  "0": {
    "property1": {
      "label": "label1",
      "value": ""
    }
    "property2": {
      "label": "label2",
      "value": "",
      "variants": {
        "0": "variant1",
        "1": "variant2"
      }
    },
    "property3": {
      "label": "label3",
      "value": ""
    }
  }
}

Then I get the data using FormData, it comes in a format that doesn't suit me:

{
    "property1": "value1",
    "property2": "variant2",
    "property3": "value3"
}

How can I bring to the desired form, that is, I need the values ​​\u200b\u200bto be set to value. In this case, it is necessary to check the current data, that is, add data to a predefined JSON but with a key one more than the last one.
How it is better to implement it? It is possible that in principle I am doing something wrong and I need it differently, I will be glad for any help, thanks!