javascript - 过滤器列表 - 根据计数键删除两个重复项中较小的一个

Question

在这个问题中，我有一个杂货 list ，我想通过删除重复项并保留只有计数较高的副本。然后还保留不重复的项目。我最终通过巧合的纯编程完成了这项工作，并且想学习解决这个问题的更好方法。我在下面评论了我的代码，以分享发生的事情和我的想法过程。如果有人有更好的方法来解决这个问题，我很乐意学习。

var groceryList = [
  {
    item: "Bananas",
    count: 4
  },
  {
    item: "Bananas",
    count: 3
  },
  {
    item: "Brussel Sprouts",
    count: 2
  },
  {
    item: "Bacon",
    count: 100
  },
  {
    item: "Beans",
    count: 19
  },
  {
    item: "Beans",
    count: 5
  }
]

const seen = {}
const newList = []
var removeDups = []
const list = groceryList.map(function(item) {
  // if we haven't this item before (via check on item name) push it into seen object
  // also push it to newList array
  if (!seen[item.item]) {
    seen[item.item] = item
    newList.push(item)
  }
  // if we have seen the item during iteration...
  else if (seen[item.item]) {
    // remove it from the newList array
    removeDups = newList.filter(function(listItem) {
      if (listItem.item == item.item) {
        console.log('matched');
      } else {
        return true
      }
    })

    // and push in the item with the higher count
    if (seen[item.item].count > item.count) {
      removeDups.push(seen[item.item])
    } else {
      removeDups.push(item)
    }
  }
})

console.log(removeDups);

Answer 1

当输入项和输出项不一定是一对一时，您可以使用 reduce 将数组简洁地转换为另一个数组(或对象):

var groceryList=[{item:"Bananas",count:4},{item:"Bananas",count:3},{item:"Brussel Sprouts",count:2},{item:"Bacon",count:100},{item:"Beans",count:19},{item:"Beans",count:5}]
const filteredListObj = groceryList.reduce((a, { item, count }) => {
  // this is a new item, or a duplicate with a greater quantity:
  if (!a[item] || a[item].count < count) a[item] = { item, count };
  return a;
}, {});
const filteredList = Object.values(filteredListObj);
console.log(filteredList);