add key:value to a .json file

I have this config.json file:

{
  "account_name": {
    "min_len": "3",
    "max_len": "15",
    "upperCase": true,
    "lowerCase": true,
    "numbers": true,
    "specialChar": false,
    "capitalize": false,
    "duplication": false,
    "startWithCapital": false
  },
  "password": {
    "min_len": "6",
    "max_len": "20",
    "upperCase": true,
    "lowerCase": true,
    "numbers": true,
    "specialChar": true,
    "capitalize": false,
    "duplication": false,
    "StartWithCapital": false
  }
}

How can I add other values to this .json file from the code? for exapmle :

var keysOpt = require('../config/config.json');
KeysOpt.name = "eric"
KeyPot.save() // will save the new field to the file itself

via Zed Evans