This sample script is for changing values by checking duplicated values of JSON for Javascript.
Please see the following script. There is an array with a JSON data with 3 keys and 3 values. It is found that the values for each element duplicate. These duplicated values are changing by adding numbers.
I use this for managing filenames. This script also can be used for Google Apps Script. If this was useful for you, I’m glad.
Script :
var data = [
    { key1: "value_a1", key2: "value_a2", key3: "value_a3" },
    { key1: "value_b1", key2: "value_a2", key3: "value_b3" },
    { key1: "value_c1", key2: "value_c2", key3: "value_b3" },
    { key1: "value_a1", key2: "value_d2", key3: "value_d3" },
    { key1: "value_e1", key2: "value_a2", key3: "value_a3" },
];
var temp = {};
for (i in data) {
    for (key in data[i]) {
        if (temp[data[i][key]]) {
            temp[data[i][key]] += 1;
            data[i][key] = data[i][key] + "_" + temp[data[i][key]].toString();
        } else {
            temp[data[i][key]] = 1;
        }
    }
}
console.log(data);
Result :
[
  {
    "key1": "value_a1",
    "key2": "value_a2",
    "key3": "value_a3"
  },
  {
    "key1": "value_b1",
    "key2": "value_a2_2",
    "key3": "value_b3"
  },
  {
    "key1": "value_c1",
    "key2": "value_c2",
    "key3": "value_b3_2"
  },
  {
    "key1": "value_a1_2",
    "key2": "value_d2",
    "key3": "value_d3"
  },
  {
    "key1": "value_e1",
    "key2": "value_a2_3",
    "key3": "value_a3_2"
  }
]