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var cityData = [
  { state: "State 1", city: "City 1", pinCode: "123456" },
  { state: "State 2", city: "City 2", pinCode: "789012" },
  { state: "State 1", city: "City 3", pinCode: "345678" },
  { state: "State 2", city: "City 4", pinCode: "901234" }
];

var stateData = {};

// Loop through the cityData array
for (var i = 0; i < cityData.length; i++) {
  var cityObj = cityData[i];
  var state = cityObj.state;
  var city = cityObj.city;
  var pinCode = cityObj.pinCode;

  // Check if the state exists in the stateData object
  if (!stateData[state]) {
    // If the state does not exist, create a new object for it
    stateData[state] = { data: [] };
  }

  // Push the city object to the state's data array
  stateData[state].data.push({ city: city, pinCode: pinCode });
}

console.log(stateData);