let library = {
id: 01,//左邊為屬性(property)，右邊為值(value)
books:{
name: 'JavaScript',
},
Sellingprice: function(){
console.log('售價:450 元');
}
}; //物件實字Object Literals
console.log(library);
//物件的建構式(另一種宣告物件的方式)
let library2 = new Object('JavaScript');
let library3 = new Object(1);
let library4 = new Object(library);
console.log(library2);
console.log(library3);
console.log(library4);
# 物件取值、新增、刪除
let library = {
id: 1,
books:{
name: 'JavaScript',
},
Sellingprice: function(){
console.log('售價:450 元');
},
'01': '00',
};
//取值
console.log(library.id);
console.log(library.books.name);
console.log(library['01']);
//新增
library.page = 100;
library['@'] = '特殊符號';
console.log(library);
//刪除
delete library.id;
delete library['01'];
delete library.page;
console.log(library);
//執行函式
library.Sellingprice();
library['Sellingprice']();
# 物件型別與純值(純值又可稱為原始型別)
//純值不能新增屬性
let city = '桃園市';
city.person = 'Kevin';
console.log(city);
let library = {};//使用物件實字的語法新增一個空物件
library.book = 'JavaScript';
console.log(library);
let fruit = [orange,];
fruit.name = 'Apple';
console.log(fruit);
function say(){//函式也是物件型別(物件型別下的子型別)
console.log('Hello');
}
say.person = 'John';
console.dir(say);//console.dir()用於顯示物件中所有屬性和屬性值
# undefined屬性預設值
let products = {
phone: 'apxxx',
}
console.log(products.id);//在物件下查找不存在的屬性，會回傳undefined
//與宣告變數比較
let a
console.log(a);//宣告a變數時，會準備一個記憶體空間給它，但是因為沒有任何值，所以出現undefined
console.log(b);//不存在b這個變數所以它會是is not defined而不是undefined
# 物件參考(參照)觀念
let a = { x:1 }; //新增一個物件就會產生一個新的記憶體空間，(此時a變數的參考路徑假設為:0x01)
let b = a; //(物件賦值是傳參考的特性，它會把參考路徑0x01賦予給b變數)
a.y = a = { x: 2 }; //新增一個物件(參考路徑假設為:0x02)，因為是同時執行，所以這邊的a.y是在原本參考路徑為0x01物件底下新增y屬性，其值是參考路徑0x02
console.log(a.y);
console.log(b);
console.log( a === b.y);
# 傳值(Call by value)
//純值修改值的時候不會有傳參考的特性
let name = 'Jay';
let name2 = name;
name2 = 'Kevin';
console.log(name, name2);
# 傳參照(Call by reference)
let library = {
book1: 'JavaScript',
book3: 'HTML',
book4: 'CSS',
}
let library2 = library;//library的參考路徑(假設為0x01)指向library2，所以當修改library2時，library物件也會被修改，因為兩者參考路徑(0x01)是一樣的
library2.book1 = 'jQuery';
console.log(library, library2);
console.log( library === library2);//參考路徑一樣所以為true
let library = {
book1: 'JavaScript',
book3: 'HTML',
book4: 'CSS',
}
let library2 = library;
library2 = {
book1: 'JavaScript',
book3: 'HTML',
book4: 'CSS',
} //library2它的參考路徑與原本會不一樣，假設library參考路徑是(0x01)，則library2是(0x02)
console.log(library, library2);
console.log( library === library2);//縱使內容一樣，但兩者參考路徑不一樣所以為false
# 傳共享物件呼叫(Call by sharing)
let library = {
book1: 'JavaScript',
book3: 'HTML',
book4: 'CSS',
}
let library2 = library;
library2 = {//重新賦值會指向新的物件
book1: 'Vue.js',
book3: 'HTML5',
book4: 'SASS',
}
console.log(library, library2);
# 淺層複製(Shallow Copy)
//因(call by reference)所以修改第二層，原本的物件也會一同被修改
const person = {
p1:
{
name: 'Tony',
money: 200,
},
p2: 'Kevin',
p3: 'John',
}
const newperson = {};
for (let key in person) {
newperson[key] = person[key];
}
newperson.p2 = 'Jay';
newperson.p1.money = 100;
console.log(person === newperson);
console.log(person, newperson);
//ES6 Object.assign()
const person = {
p1:
{
name: 'Tony',
money: 200,
},
p2: 'Kevin',
p3: 'John',
}
let newperson = Object.assign({}, person);
newperson.p2 = 'charly';
newperson.p1.money = 50;
console.log(person, newperson);
//ES6 spread operator
const person = {
p1:
{
name: 'Tony',
money: 200,
},
p2: 'Kevin',
p3: 'John',
}
let newperson = {...person};
newperson.p2 = 'charly';
newperson.p1.money = 50;
console.log(person, newperson);
# 深層複製(Deep copy)
const person = {
p1:
{
name: 'Tony',
money: 200,
},
p2: 'Kevin',
p3: 'John',
}
let newperson = JSON.parse(JSON.stringify(person));
newperson.p2 = 'charly';
newperson.p1.money = 50;
console.log(person, newperson);
# 陣列(Array)
# push
const book = [
{
b1: 'JavaScript',
},
{
b2: 'Python',
},
{
b3: 'Node.js',
},
]
book.push('JAVA');
console.log(book);
# pop
const book = [
{
b1: 'JavaScript',
},
{
b2: 'Python',
},
{
b3: 'Node.js',
},
]
book.pop();
console.log(book);
# unshift
const book = [
{
b1: 'JavaScript',
},
{
b2: 'Python',
},
{
b3: 'Node.js',
},
]
book.unshift('jQuery');
console.log(book);
# shift
const book = [
{
b1: 'JavaScript',
},
{
b2: 'Python',
},
{
b3: 'Node.js',
},
]
book.shift();
console.log(book);
# 陣列length須注意的小地方
const book = [
{
b1: 'JavaScript',
},
{
b2: 'Python',
},
{
b3: 'Node.js',
},
]
book.b0 = 1;//新增一個屬性b0其值為1，可以看到輸出結果並不會增加陣列的長度
console.log(book.length);//3
book[4] = {b4:'jQuery'};
console.log(book);
console.log(book[3]);//使用中括號新增值的時候，中間略過的會補上空值(undefined)
