如何访问数组中对象的数组？

Question

[
    {
        name:"Technology",
        logoImage:require("../../assets/g837.png"),
        subCategory:[
            "IT",
            "Networks",
            "Appliances",
            "Industrial Machines",
            "Medical technology",
            "robotics",
            "AI",
            "Electronics",
            "Explosives",
            "Machinery", 
            "Cryptocurrency",
            "Electric Vehicles",
            "Biotechnology"

        ]
    },
    {
        name:"Business",
        logoImage:require("../../assets/business.png"),
        subCategory:[
            "Industries",
            "Economics",
            "Journalism",
            "Labor",
            "Law",
            "Real estate",
            "Entrepreneurship",
            "Investment",
            "Banking",
            "Leadership",
            "Advertising",
            "Business Strategy", 
            "Marketing",
            "E-commerce"
        ]
    },
    {
        name:"Entertainment",
        logoImage:require("../../assets/entertainment.png"),
        subCategory:[
            "Comedy",
            "Dance",
            "Dramas",
            "Films",
            "Gaming",
            "Toys",
            "Gambling",
            "Comics",
            "Social sites"

        ]
    }
]

Answer 1

假设用于存储JSON的变量名为dataSet，您将执行以下操作

for(data of dataSet){
    console.log(data.subCategory)
}

在这个for循环中，您还可以遍历数组的所有subCategory。

Answer 2

​

const myArray = [
    {
        "subCategory":[
            "IT",
            "Networks"
        ]
    },
    {
        "subCategory":[
            "IT",
            "Networks"
        ]
    }
]

myArray.forEach((eachObject) => {
  console.log(eachObject.subCategory)
})

​

假设您已将该数组存储在一个变量myArray中

然后，可以在forLoop的帮助下轻松地迭代subCategory的值。

myArray.forEach((eachObject) => {
    console.log(eachObject.subCategory)
})

Answer 3

如果这只是一个简单的JS问题，那么访问数组/对象中的一些数据...

用于访问数组内元素的：

array[index] // first element start from 0.

上面的“元素”可以看作是字符串、数字、对象，甚至是数组中的数组。

访问object内部元素的：

let obj = {a:100,b:200,c:300}

object.key //obj.a means will get the value of 100

或

object["key"] //obj["b"] means will get the value of 200

或

let x = "c"

object[variable] // obj[x] is equal to obj["c"] means will get the value of 300.

因此，要从对象数组内部的数组访问"subCategory“，您只需组合上面的策略：

var nestedArray = [
    {
        name:"Technology",
        logoImage:require("../../assets/g837.png"),
        subCategory:[
            "IT",
            "Networks",
            "Appliances",
            "Industrial Machines",
            "Medical technology",
            "robotics",
            "AI",
            "Electronics",
            "Explosives",
            "Machinery", 
            "Cryptocurrency",
            "Electric Vehicles",
            "Biotechnology"

        ]
    },
    {
        name:"Business",
        logoImage:require("../../assets/business.png"),
        subCategory:[
            "Industries",
            "Economics",
            "Journalism",
            "Labor",
            "Law",
            "Real estate",
            "Entrepreneurship",
            "Investment",
            "Banking",
            "Leadership",
            "Advertising",
            "Business Strategy", 
            "Marketing",
            "E-commerce"
        ]
    },
    {
        name:"Entertainment",
        logoImage:require("../../assets/entertainment.png"),
        subCategory:[
            "Comedy",
            "Dance",
            "Dramas",
            "Films",
            "Gaming",
            "Toys",
            "Gambling",
            "Comics",
            "Social sites"
        ]
    }
]


var subCategoryArray = nestedArray[0]["subCategory"] // return  ["IT", "Networks",...]

循环如果数组中有多个对象，则需要使用：

var subCategoryArray = []
for(var i = 0; i < nestedArray.length; i++){
   subCategoryArray= subCategoryArray.concat(nestedArray[i]["subCategory"])
}

console.log(subCategoryArray) //return ["IT", "Networks",...,"Comics","Social sites"]