如何删除数组中的多个对象？

Question

我有这样一个数组：

const myArray = [ 
  {
    title: 'title',
    category: 'genetic-diseases'
  },
  {
    title: 'title',
    category: 'genetic-disorders'
  },
  { title: 'title', category: 'genetic-disorders' },
  {
    title: 'title',
    category: 'genetic-disorders'
  },
  {
    title: 'title',
    category: 'genetic-mutation'
  },
  {
    title: 'title',
    category: 'genetic-mutation'
  },
  {
    title: 'title',
    category: 'genetic-mutation'
  }
]

我只想要数组中每个类别对象中的两个，如果该类别的对象数超过2，则删除其余的对象，并得到如下所示：

const myArray = [ 
  {
    title: 'title',
    category: 'genetic-diseases'
  },
  { title: 'title', category: 'genetic-disorders' },
  {
    title: 'title',
    category: 'genetic-disorders'
  },
  {
    title: 'title',
    category: 'genetic-mutation'
  },
  {
    title: 'title',
    category: 'genetic-mutation'
  }
]

如果数组中的对象数量超过2，如何删除特定类别的其余对象？

Answer 1

    const myArray = [ 
    {
    title: 'title',
    category: 'genetic-diseases'
    },
    {
    title: 'title',
    category: 'genetic-disorders'
    },
    { title: 'title', category: 'genetic-disorders' },
    {
    title: 'title',
    category: 'genetic-disorders'
    },
    {
    title: 'title',
    category: 'genetic-mutation'
    },
    {
    title: 'title',
    category: 'genetic-mutation'
    },
    {
    title: 'title',
    category: 'genetic-mutation'
    }
    ];
    
    var categoryQuantities = {}; //counts how many objects from each category entered the filtered array
    var filteredArray = []; //array with first 2 objects from each categoty
    for (var obj of myArray) {
        var category = obj.category;
        if (category in categoryQuantities) {
            categoryQuantities[category]++;
        } else {
            categoryQuantities[category] = 1;
        }
        
        if (categoryQuantities[category] <= 2) {
            filteredArray.push(obj);
        }
    }
    
    console.log(filteredArray);

最后一个数组位于'filteredArray‘中。原始数组没有更改，因此您可能要执行以下操作：

    myArray = filteredArray;

Answer 2

基本上我做了两个阶段。首先，我按类别分组(每个类别最多2项)，然后我将其夷平。我把它变成了一个名为group_by_at_most的通用函数

​

var myArray = get_data();

var result = group_by_at_most(myArray, 'category', 2);
console.log(result);

function group_by_at_most(myArray, by, at_most) {
  var obj = {}

  myArray.forEach(function(item) {
    if (!obj[item[by]]) {
      obj[item[by]] = []
    }
    if (obj[item[by]].length < at_most) {
      obj[item[by]].push(item);
    }
  })

  var result = [];
  for (var key in obj) {
    var items = obj[key];
    result.push(...items);
  }

  return result;
}



function get_data() {
  return [{
      title: 'title',
      category: 'genetic-diseases'
    },
    {
      title: 'title',
      category: 'genetic-disorders'
    },
    {
      title: 'title',
      category: 'genetic-disorders'
    },
    {
      title: 'title',
      category: 'genetic-disorders'
    },
    {
      title: 'title',
      category: 'genetic-mutation'
    },
    {
      title: 'title',
      category: 'genetic-mutation'
    },
    {
      title: 'title',
      category: 'genetic-mutation'
    }
  ]
}

.as-console-wrapper {
  max-height: 100% !important;
}

​