使用javascript从以下对象获取Key值对

Question

我正在学习JavaScript，这可能是一个基本问题，请帮助我在下面获得成果。

我正在像下面这样在obejct中构造一个数组以便稍后使用数据。现在，我必须将类别作为“帮助”发送，并且需要动态获取所有子类别的值。

[ 
    {"category":"Help","subcategory":"Email"}, 
    {"category":"Help","subcategory":"application"}, 
    {"category":"Help","subcategory":"Software"}, 
    {"category":"Help","subcategory":"Hardware"}, 
    {"category":"Request","subcategory":"Access"}, 
    {"category":"Request","subcategory":"Remote"}, 
    ] 

在此先感谢

Answer 1

你可以用Array#filter先过滤，然后用Array#map得到的值。

var array = [{ category: "Help", subcategory: "Email" }, { category: "Help", subcategory: "application" }, { category: "Help", subcategory: "Software" }, { category: "Help", subcategory: "Hardware" }, { category: "Request", subcategory: "Access" }, { category: "Request", subcategory: "Remote" }], 
 
    subcategory = array 
 
     .filter(a => a.category === 'Help') 
 
     .map(a => a.subcategory); 
 
    
 
console.log(subcategory);

.as-console-wrapper { max-height: 100% !important; top: 0; }

ES5

var array = [{ category: "Help", subcategory: "Email" }, { category: "Help", subcategory: "application" }, { category: "Help", subcategory: "Software" }, { category: "Help", subcategory: "Hardware" }, { category: "Request", subcategory: "Access" }, { category: "Request", subcategory: "Remote" }], 
 
    subcategory = array 
 
     .filter(function (a) { return a.category === 'Help'; }) 
 
     .map(function (a) { return a.subcategory; }); 
 
    
 
console.log(subcategory);

.as-console-wrapper { max-height: 100% !important; top: 0; }

Answer 2

您应该使用filter方法，以实现这一目标。

此外，使用map方法为了创建一个新的数组只与subcategories。

var array=[ 
 
    {"category":"Help","subcategory":"Email"}, 
 
    {"category":"Help","subcategory":"application"}, 
 
    {"category":"Help","subcategory":"Software"}, 
 
    {"category":"Help","subcategory":"Hardware"}, 
 
    {"category":"Request","subcategory":"Access"}, 
 
    {"category":"Request","subcategory":"Remote"}, 
 
]; 
 

 
var subcategories = array.filter(a => a.category === "Help").map(a => a.subcategory); 
 
console.log(subcategories);

.as-console-wrapper { max-height: 100% !important; top: 0; }