计算对象字段在数组中的出现次数，并将其添加为附加键

function calculateFieldOccurrences(arr, field) {
  var occurrences = {};

  for (var i = 0; i < arr.length; i++) {
    var obj = arr[i];
    if (obj.hasOwnProperty(field)) {
      var value = obj[field];
      if (occurrences.hasOwnProperty(value)) {
        occurrences[value]++;
      } else {
        occurrences[value] = 1;
      }
    }
  }

  return occurrences;
}

// 示例用法
var arr = [
  { name: 'Alice', age: 25 },
  { name: 'Bob', age: 30 },
  { name: 'Alice', age: 25 },
  { name: 'Charlie', age: 35 }
];

var fieldOccurrences = calculateFieldOccurrences(arr, 'name');
console.log(fieldOccurrences);