Question

*注意：我正在寻找Vanilla JS（没有jQuery）的解决方案，最好不是for循环。

我有一个简单的JSON数据集，我想在其中将每个“类型”推入字符串数组中。

[
{
    "type": "Fruits",
    "objects": 
    [
        {"name": "Apples", "qty":35},
        {"name": "Bananas", "qty":48},
        {"name": "Oranges", "qty":12}
    ]
},

{
    "type": "Vegetables",
    "objects": 
    [
        {"name": "Celery", "qty":255},
        {"name": "Potatos", "qty":105},
        {"name": "Carrots", "qty":483},
        {"name": "Peas", "qty":350}
    ]
},

{
    "type": "Meats",
    "objects": 
    [
        {"name": "Lamb", "qty":255},
        {"name": "Chicken", "qty":545},
        {"name": "Beef", "qty":13}
    ]
}
]

输出应为： ["Fruits", "Vegetables", "Meats"]

我将JSON对象解析为一个变量（有效），但是我不明白为什么简单的filter函数不起作用：

var myData = require("../data.json");
console.log(myData);  // <-- Yay! I have my data

//Retrieve all "type" strings into an array (** this isn't working **)
var myTypes = myData.filter(a => a.type);
console.log(myTypes);  // <-- This shows an array of objects (like above) and not an array of string "type"

Answer 1

您可以使用map代替filter

const items = [
  {
    "type": "Fruits",
    "objects": 
    [
      {"name": "Apples", "qty":35},
      {"name": "Bananas", "qty":48},
      {"name": "Oranges", "qty":12}
    ]
  },

  {
    "type": "Vegetables",
    "objects": 
    [
      {"name": "Celery", "qty":255},
      {"name": "Potatos", "qty":105},
      {"name": "Carrots", "qty":483},
      {"name": "Peas", "qty":350}
    ]
  },

  {
    "type": "Meats",
    "objects": 
    [
      {"name": "Lamb", "qty":255},
      {"name": "Chicken", "qty":545},
      {"name": "Beef", "qty":13}
    ]
  }
]

const types = items.map(item => item.type)

console.log(types)

// [ 'Fruits', 'Vegetables', 'Meats' ]

Answer 2

您应该使用map而不是filter：

var data = [
{
    "type": "Fruits",
    "objects": 
    [
        {"name": "Apples", "qty":35},
        {"name": "Bananas", "qty":48},
        {"name": "Oranges", "qty":12}
    ]
},

{
    "type": "Vegetables",
    "objects": 
    [
        {"name": "Celery", "qty":255},
        {"name": "Potatos", "qty":105},
        {"name": "Carrots", "qty":483},
        {"name": "Peas", "qty":350}
    ]
},

{
    "type": "Meats",
    "objects": 
    [
        {"name": "Lamb", "qty":255},
        {"name": "Chicken", "qty":545},
        {"name": "Beef", "qty":13}
    ]
}
]

console.log(data.map((obj) => obj.type))

Answer 3

使用map函数。

console.log(array.map(a => a.type));

按键值将JSON对象过滤为字符串数组

3 个答案: