解構賦值

Node.js 解構賦值
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取得陣列指定位置資料

let Employee = ['Kay', 'Jay'];
let [Kay, Jay] = Employee;

// [ 'Kay', 'Jay' ]
console.log(Employee);
// Kay
console.log(Kay);
// Jay
console.log(Jay);

取得陣列指定位置資料，忽略其中幾個數值

沒有要指定的資料，使用 逗號隔開但留空，不指定變數

let Employee = ['Kay', 'Jay'];
let [, Jay] = Employee;

// [ 'Kay', 'Jay' ]
console.log(Employee);
// Jay
console.log(Jay);

單行定義變數

不建議使用，當變數越多，導致程式可讀性不高

let [Kay, Jay] = ['Kay', 'Jay'];
// Kay
console.log(Kay);
// Jay
console.log(Jay);

交換變數數值

let name = 'KJ';
let age = 17;

// My name is KJ, my age is 17
console.log(`My name is ${name}, my age is ${age}`);
// 交換變數數值
[name, age] = [age, name];
// My name is 17, my age is KJ
console.log(`My name is ${name}, my age is ${age}`);

取得物件中指定鍵值的變數值

const Employee = {
    name : 'KJ',
    age: 17
};
// 取得物件中指定鍵值的變數值
const {name, age} = Employee;
// { name: 'KJ', age: 17 }
console.log(Employee);
// KJ
console.log(name);
// 17
console.log(age);

物件屬性賦值

若鍵值相同，直接將變數傳入物件中，變數名稱即為鍵值名稱

const name = 'KJ';
const age = 17;
let Employee = {
    name,
    age
};
// { name: 'KJ', age: 17 }
console.log(Employee);

若鍵值有要異動，則就在前方加入鍵值名稱即可

const name = 'KJ';
const age = 17;
let Employee = {
    newName : name,
    age
};
// { newName: 'KJ', age: 17 }
console.log(Employee);

取得指定數值，並重設其他屬性到新變數

const Employee = {
    name : 'KJ',
    age: 17,
    height: 199
};
// 取得指定數值，並重設其他屬性到新變數
const {age, ...OtherEmployee} = Employee;

// 17
console.log(age);
// { name: 'KJ', height: 199 }
console.log(OtherEmployee);
// { name: 'KJ', age: 17, height: 199 }
console.log(Employee);

用於傳遞物件參數

const SayHi = ({name, ...other}) => {
    // KJ
    console.log(name);
    // { age: 17, height: 199 }
    console.log(other);
};

SayHi({
    name : 'KJ',
    age: 17,
    height: 199
})

擴展物件數值

const Employee = {
    name : 'KJ',
    age: 17,
};

const NewEmployee = {
    ...Employee,
    height: 199
};

// { name: 'KJ', age: 17 }
console.log(Employee);
// { name: 'KJ', age: 17, height: 199 }
console.log(NewEmployee);

連續等於

會先從 後面 賦值，才往前賦值

NewEmployee = Employee = Person = {...}