使用javascript從以下對象獲取Key值對

Question

我正在學習JavaScript，這可能是一個基本問題，請幫助我在下面獲得成果。

我正在像下面這樣在obejct中構造一個數組以便稍後使用數據。現在，我必須將類別作爲「幫助」發送，並且需要動態獲取所有子類別的值。

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

在此先感謝

Answer 1

你可以用Array#filter先過濾，然後用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

您應該使用filter方法，以實現這一目標。

此外，使用map方法爲了創建一個新的數組只與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; }