Creating object array from key-value pairs

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Alternative 1
 
var values = [
  {'Group': 'A', 'Key': 'Name', 'Value': 'John'},
  {'Group': 'A', 'Key': 'Age', 'Value': '30'},
  {'Group': 'A', 'Key': 'City', 'Value': 'London'},
  {'Group': 'B', 'Key': 'Name', 'Value': 'Hans'},
  {'Group': 'B', 'Key': 'Age', 'Value': '35'},
  {'Group': 'B', 'Key': 'City', 'Value': 'Berlin'},
  {'Group': 'C', 'Key': 'Name', 'Value': 'José'},
  {'Group': 'C', 'Key': 'Age', 'Value': '25'},
  {'Group': 'C', 'Key': 'City', 'Value': 'Madrid'}
];

var map = {};
values.forEach(function(value) {
  map[value.Group] = map[value.Group] || {Group: value.Group};
  map[value.Group][value.Key] = value.Value;
});

var results = Object.keys(map).map(function(key) { return map[key]; });
 
 pending…
Alternative 2
 
var values = [
  {'Group': 'A', 'Key': 'Name', 'Value': 'John'},
  {'Group': 'A', 'Key': 'Age', 'Value': '30'},
  {'Group': 'A', 'Key': 'City', 'Value': 'London'},
  {'Group': 'B', 'Key': 'Name', 'Value': 'Hans'},
  {'Group': 'B', 'Key': 'Age', 'Value': '35'},
  {'Group': 'B', 'Key': 'City', 'Value': 'Berlin'},
  {'Group': 'C', 'Key': 'Name', 'Value': 'José'},
  {'Group': 'C', 'Key': 'Age', 'Value': '25'},
  {'Group': 'C', 'Key': 'City', 'Value': 'Madrid'}
];

var group, results = [];
for (var i = 0; i < values.length; ) {
  results.push({Group: group = values[i].Group});
  do {
    results[results.length - 1][values[i].Key] = values[i].Value;  
  } while (++i < values.length && values[i].Group == group);
}
 
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