如何计算对象中特定元素的数量？答案

【问题标题】：How to count a number of specific elements in an object?如何计算对象中特定元素的数量？
【发布时间】：2020-04-27 03:47:54
【问题描述】：

我有一组物品fruitItems，看起来像这样：

[
    {
        "name": "banana",
        "origID": "7064012136"
    },
    {
        "name": "apple",
        "origID": "8390108418"
    },
    {
        "name": "pineapple",
        "origID": "8317598430"
    },
    {
        "name": "banana",
        "origID": "8395091043"
    },
    {
        "name": "orange",
        "origID": "8391923474"
    }
]

如何获取此列表中banana 的编号？我试过这样做：

fruitItems.name.filter(x => x === "banana").length;

但它会抛出ReferenceError: fruitItems is not defined，即使它已定义。

【问题讨论】：

你也可以发布定义
fruitItems.filter(x => x.name === 'banana').length;
是的，我把.name放错地方了，非常感谢

标签： javascript object numbers filtering counting

【解决方案1】：

更干净的解决方案:)

const fruits = [{
  "name": "banana",
  "origID": "7064012136"
}, {
  "name": "apple",
  "origID": "8390108418"
}, {
  "name": "pineapple",
  "origID": "8317598430"
}, {
  "name": "banana",
  "origID": "8395091043"
}, {
  "name": "orange",
  "origID": "8391923474"
}];


const count = fruits.reduce((acc, {
  name
}) => name === 'banana' ? acc + 1 : acc, 0); //2

console.log(count)

【讨论】：

【解决方案2】：

语法修正：

const data = [{
    "name": "banana",
    "origID": "7064012136"
  },
  {
    "name": "apple",
    "origID": "8390108418"
  },
  {
    "name": "pineapple",
    "origID": "8317598430"
  },
  {
    "name": "banana",
    "origID": "8395091043"
  },
  {
    "name": "orange",
    "origID": "8391923474"
  }
]

const res = data.filter(({
  name
}) => name === "banana").length;

console.log(res)

【讨论】：