将计数值添加到具有相同键值的对象（对象数组）

Question

您好，我需要对对象数组进行复杂的迭代。我有这样的数组：

[ 
  { name: 'Jacob', lastName: 'Smith', dob: '1995-11-29' },
  { name: 'Jacob', lastName: 'Smith', dob: '1991-08-21' },
  { name: 'Ann', lastName: 'Smith', dob: '1995-11-29' },
  { name: 'Ann', lastName: 'Nansen', dob: '1983-01-01' },
  { name: 'Jacob', lastName: 'Smith', dob: '1985-06-15' },
  { name: 'Jacob', lastName: 'Smith', dob: '1995-11-29' },
  { name: 'Ann', lastName: 'Smith', dob: '2010-11-29' },
]

我想向每个对象添加 count 属性来计算具有相同名称和姓氏的对象...所以现在应该是：

[ 
  { name: 'Jacob', lastName: 'Smith', count: 4 },
  { name: 'Ann', lastName: 'Smith', count: 2 },
  { name: 'Ann', lastName: 'Nansen', count: 1' },
]

Answer 1

您可以使用Array.reduce和Object.values

• 转换对象中的数组，其中键作为名称，姓氏组合，值作为结果对象。
• 从对象中，获取所有值作为最终结果

let arr = [{ name: 'Jacob', lastName: 'Smith', dob: '1995-11-29' },{ name: 'Jacob', lastName: 'Smith', dob: '1991-08-21' },{ name: 'Ann', lastName: 'Smith', dob: '1995-11-29' },{ name: 'Ann', lastName: 'Nansen', dob: '1983-01-01' },{ name: 'Jacob', lastName: 'Smith', dob: '1985-06-15' },{ name: 'Jacob', lastName: 'Smith', dob: '1995-11-29' },{ name: 'Ann', lastName: 'Smith', dob: '2010-11-29' }];

let result = Object.values(arr.reduce((a,{name, lastName}) => {
  let key = `${name}_${lastName}`;
  a[key] = a[key] || {name, lastName, count : 0};
  a[key].count++;
  return a;
}, {}));

console.log(result);