使用javascript从下面的对象获取键值对

Question

我正在学习 javascript，这可能是一个基本问题，请帮助我实现以下目标。

我正在像下面这样在 obejct 中构造一个数组，以便以后使用数据。现在，我必须将类别作为“帮助”发送，并且需要动态获取它的所有子类别值。

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

提前致谢

Answer 1

您可以先使用Array#filter 过滤，然后使用Array#map 获取值。

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 方法来实现这一点。

另外，使用map 方法以便仅使用subcategories 创建一个新数组。

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; }