Arrays

playground.json

{
    "scripts": [],
    "showConsole": true,
    "template": true
}

script.js

const prefs = [
  {
    "Type": "TestType1",
    "Key": "key4",
    "Value": {
      "key": "updated value"
    }
  },
  {
    "Type": "FleetOrder",
    "Key": "FleetOrder",
    "Value": {
      "FleetOrder": [
        32,
        93,
        31,
        333,
        2444,
        2575
      ]
    }
  },
  {
    "Type": "TestType1",
    "Key": "key3",
    "Value": {
      "key": "updated value"
    }
  },
  {
    "Type": "TestType1",
    "Key": "key1",
    "Value": {
      "key": "Test a new value"
    }
  }
]


const testTypeObject = prefs.filter( x => x.Type === 'TestType1' );
const testType = testTypeObject[0].Value;

const fleetOrderObject = prefs.filter( x => x.Value.FleetOrder );
const fleetOrder = fleetOrderObject[0].Value;

const userPrefs = { ...fleetOrder, ...testType };

console.dir( JSON.stringify(userPrefs) );