create nested object from object of arrays

How can I take an array of objects like this:

let data = [
    {
        "FirstName": "TRACY",
        "Code": "CCI41",
        "UtilName": "Cable",
        "gridid": 570
    },
    {
        "FirstName": "ANGELA",
        "Code": "TWCZ40",
        "UtilName": "Cable",
        "gridid": 570
    },
    {
        "FirstName": "WILFORD",
        "Code": "TCE12",
        "UtilName": "Electric",
        "gridid": 570
    },
    {
        "FirstName": "COREY",
        "Code": "SCEJZ40",
        "UtilName": "Electric",
        "gridid": 570
    },
    {
        "FirstName": "ERNEST",
        "Code": "SGRAZ01",
        "UtilName": "Fiber",
        "gridid": 570
    },
    {
        "FirstName": "WILFORD",
        "Code": "TCE12",
        "UtilName": "Fiber",
        "gridid": 570
    },
    {
        "FirstName": "COREY",
        "Code": "SCGZ02",
        "UtilName": "Gas",
        "gridid": 570
    },
    {
        "FirstName": "ANGELO",
        "Code": "BSZT29",
        "UtilName": "Phone",
        "gridid": 570
    }
]

And turn it to an array like this that contains grouped per gridid per UtilName:

let newArr = [
  {
    570: [
      {
        "Cable": [
          {
            "FirstName": "Tracey",
            "Code": "CCI41"
          }, {
            "FirstName": "ANGELA",
            "Code": "TWCZ40"
          }
        ],
        "Electric": [
          {
            "FirstName": "WILFORD",
            "Code": "TCE12"
          }, {
            "FirstName": "COREY",
            "Code": "SCEJZ40"
          }
        ],
        "Fiber": [
          {
            "FirstName": "WILFORD",
            "Code": "TCE12"
          }
        ],
        "Gas": [
          {
            "FirstName": "COREY",
            "Code": "SCGZ02"
          }
        ],
        "Phone": [
          {
            "FirstName": "ANGELO",
            "Code": "BSZT29"
          }
        ]
      }
    ]
  }
]

It can be structured in alternative ways but the goal is to get each person grouped into a gridid and UtilName.

>Solution :

let data = [
    {"FirstName": "TRACY","Code": "CCI41","UtilName": "Cable","gridid": 570},
    {"FirstName": "ANGELA","Code": "TWCZ40","UtilName": "Cable","gridid": 570},
    {"FirstName": "WILFORD","Code": "TCE12","UtilName": "Electric","gridid": 570},
    {"FirstName": "COREY","Code": "SCEJZ40aa","UtilName": "Electric","gridid": 570},
    {"FirstName": "COREY","Code": "SCEJZ40","UtilName": "Electric","gridid": 580},
    {"FirstName": "COREY","Code": "SCEJZ40a","UtilName": "Electric","gridid": 580}
];

let expected_output = {}
data.forEach(elem => {
  if(!(elem['gridid'] in expected_output)){
    expected_output[elem['gridid']] = [{}]
  }
  if(!(elem['UtilName'] in expected_output[elem['gridid']][0])){
    expected_output[elem['gridid']][0][elem['UtilName']] = []
  }
  const j = expected_output[elem['gridid']][0][elem['UtilName']].length
  expected_output[elem['gridid']][0][elem['UtilName']][j] = {'FirstName' : elem['UtilName'],'Code' : elem['Code']}
});

console.log(expected_output)