如何访问对象的值？

Question

我试图循环一组对象，并获得第一个值(繁殖)。比如：

• 比格
• 金毛猎犬
• 柯尔基
• 金多丽
• 拉布拉多猎犬

现在，我对数据进行了映射，但它只列出了每个{}。如何访问每个{}的内部？

const data = [
    { 
        "breed": "Beagle",
        "characteristics": "playful" 
    },
    {
        "breed": "Golden Retriever", 
        "characteristics": "calm" 
    },
    {
        "breed": "Corgi", 
        "characteristics": "bright" 
    },
    {
        "breed": "Goldendoodle", 
        "characteristics": "gentle" 
    },
    {
        "breed": "Labrador Retriever", 
        "characteristics": "loyal" 
    },
]


data.map(item => {
    console.log(item);
})
// Object { breed: "Beagle", characteristics: "playful" }, Object { breed: "Golden Retriever", characteristics: "calm" }, ...

Answer 1

为了获得品种，从每个项目中提取breed。

​

const data = [{"breed":"Beagle","characteristics":"playful"},{"breed":"Golden Retriever","characteristics":"calm"},{"breed":"Corgi","characteristics":"bright"},{"breed":"Goldendoodle","characteristics":"gentle"},{"breed":"Labrador Retriever","characteristics":"loyal"}];

const res = data.map(({ breed }) => breed);
console.log(res);

​

ES5语法：

​

var data = [{"breed":"Beagle","characteristics":"playful"},{"breed":"Golden Retriever","characteristics":"calm"},{"breed":"Corgi","characteristics":"bright"},{"breed":"Goldendoodle","characteristics":"gentle"},{"breed":"Labrador Retriever","characteristics":"loyal"}];

var res = data.map(function(item) {
  return item.breed
});
console.log(res);

​

如果您只想记录每一项，请使用forEach循环：

​

const data = [{"breed":"Beagle","characteristics":"playful"},{"breed":"Golden Retriever","characteristics":"calm"},{"breed":"Corgi","characteristics":"bright"},{"breed":"Goldendoodle","characteristics":"gentle"},{"breed":"Labrador Retriever","characteristics":"loyal"}];

data.forEach(({ breed }) => console.log(breed));

​

Answer 2

简单地说：

data.map(item => {
    console.log(item.breed);
})