# [JavaScript] Object

###### tags: `JavaScript`

## 判斷屬性是否存在
* `hasOwnProperty()`
* `obj.hasOwnProperty('hasOwnProperty');`
* 只檢查物件本身的屬性
* `in`
* `'hasOwnProperty' in obj;`
* 會往上檢查物件的原型鏈

## 取值、新增、刪除

var book = {
  name: '書名',
  author: '作者',
  price: '350',
  isbn: '9789861234567',
  eeee: 'eeee',
  details: {
    publisher: '出版社',
    publicationDate: '2020/12/09',
    binding: '紙本平裝'
  },
  promotions: function() {
    return '參與全站滿千折百活動'
  },
  '$-name': '特殊屬性名稱',
}

// 取值 
console.log(book.name); // 書名
console.log(book['$-name']); // 特殊屬性名稱
console.log(book.promotions()); // 參與全站滿千折百活動
console.log(book['promotions']()); // 參與全站滿千折百活動

// 新增
book.pages = '450';
book['details']['language'] = '中文';

// 刪除
delete book.eeee;
delete book['$-name'];

console.log(book);

## Shallow Copy（淺層複製）與 Deep Copy（深層複製）

var book = {
  name: '書名',
  author: '作者',
  details: {
    publisher: '出版社',
    publicationDate: '2020/12/09',
  }
}

// Shallow Copy 淺層複製 - for in
var book2 = {};
for (var key in book) {
 book2[key] = book[key];
}
console.log(book === book2); // false
console.log(book.details === book2.details); // true

// Shallow Copy 淺層複製 - jQuery
var book3 = jQuery.extend({}, book);
console.log(book === book3); // false
console.log(book.details === book3.details); // true

// Shallow Copy 淺層複製 - ES6
var book4 = Object.assign({}, book);
console.log(book === book4); // false
console.log(book.details === book4.details); // true

// Deep Copy 深層複製 - JSON.parse & JSON.stringify
var book5 = JSON.parse(JSON.stringify(book));
console.log(book === book5); // false
console.log(book.details === book5.details); // false

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:::info
建立日期：2020-12-23
更新日期：2020-12-23
:::