ES6NewDragon.js

let person = {name: 'John Smith'};
let tpl = `My name is ${person.name}.`;
console.log(tpl);

let x = 5;
let y =3;
let tpl2 = `${x} + ${y} = ${x+y}`;
console.log(tpl2);

// template literal本身不具重用性，除非自己包成函式
let tpl3 = (x,y) => `${x} + ${y} = ${x+y}`
let four = tpl3(2,2);
console.log(four);

//Destructure
var data = {x:1, y:2};
var data2 = {...data, z:3};
console.log(data2); // Object {x: 1, y: 2, z: 3}

//注意用法，這邊會取出字串長度
const {length} = "Wth?";
console.log(length);

//有時候不好讀
const employee = {
	name: "Woo",
  	address:{
    	countruy:"TW",
      	state:"Taipei"
    },
  	favorateNumber:[11,22,33,44]
}

//state : Taipei, second: 22
const {
	name, address:{state}, favorateNumber:[,second]
} = employee;

const data4 = null;
let data3 = {...data4?data4:{default:true}}
console.log(data3)

const constX = 3;
//Error: constX is read-only
//constX = 4;

// 關於Const

const arr = [1,2,3];
arr.push(4);
console.log(arr); // 4還是加上去了！因為Array是Mutable

//解法
Object.freeze(arr);
//arr.push(4);  Error:Can't add property 4, object is not extensible
=========

let person = {name: 'John Smith'};
let tpl = `My name is ${person.name}.`;
console.log(tpl);

let x = 5;
let y =3;
let tpl2 = `${x} + ${y} = ${x+y}`;
console.log(tpl2);

// template literal本身不具重用性，除非自己包成函式
let tpl3 = (x,y) => `${x} + ${y} = ${x+y}`
let four = tpl3(2,2);
console.log(four);

//Destructure
var data = {x:1, y:2};
var data2 = {...data, z:3};
console.log(data2); // Object {x: 1, y: 2, z: 3}

//注意用法，這邊會取出字串長度
const {length} = "Wth?";
console.log(length);

//有時候不好讀
const employee = {
	name: "Woo",
  	address:{
    	countruy:"TW",
      	state:"Taipei"
    },
  	favorateNumber:[11,22,33,44]
}

//state : Taipei, second: 22
const {
	name, address:{state}, favorateNumber:[,second]
} = employee;

const data4 = null;
let data3 = {...data4?data4:{default:true}}
console.log(data3)

const constX = 3;
//Error: constX is read-only
//constX = 4;

// 關於Const

const arr = [1,2,3];
arr.push(4);
console.log(arr); // 4還是加上去了！因為Array是Mutable

//解法
Object.freeze(arr);
//arr.push(4);  Error:Can't add property 4, object is not extensible

//創建 Array
let arr1 = Array(1,2,3);
let arr2 = Array(10); //產生長度為十的空陣列
let arr3 = Array.of(10);
let arr4 = Array.from({length:5}, (v,k)=> k*2);//0,2,4,6,8
console.log(arr1, arr2, arr3, arr4);// 1,2,3 //,,,,,,,,, //10 //0,2,4,6,8

//關於Set
let x = new Set([1, 2, 3, 4, 4, 4, 5]);

x.add(6);
x.delete(2);

console.log('The set contains', x.size, 'elements.');
console.log('The set has 1:', x.has(1));
console.log('The set has 8:', x.has(8));

//values and keys are the same in a set
x.forEach((value, key, set) => console.log(value, key, set));

//簡單的Map
const map = new Map([[1,"hello"], ['2', "world"]]);
console.log(map.get('2'));


=====
	//兩者在操作上是等價的
class Polygon1 {
	constructor(height, width) { //class constructor
		this.name = 'Polygon';
		this.height = height;
		this.width = width;
	}

	sayName() { //class method
		console.log('Hi, I am a', this.name + '.');
	}
}

// De-sugar
let Polygon2 = function(height, width){
	this.name = 'Polygon2';
	this.height = height;
  	this.width = width;
}

Polygon2.prototype = {
  sayName: function(){
	console.log('Hi, I am a', this.name + '.');
  }
}

let p1 = new Polygon1(100,100);
let p2 = new Polygon2(100,100);
console.log(p1, p2);

//查看所有屬性
let name = [];
for(let n in new Polygon1()){
	name.push(n);
}
console.log(name);
name = [];
for(let n in new Polygon2()){
	name.push(n);
}
console.log(name)
//可以看到 宣告class的少了function，需要換另一個方式
//Object.getPrototypeOf() 回傳指定物件的原型，換句話說，就是取得該物件的 [[Prototype]] 屬性的值).
// Object.getOwnPropertyNames() 以陣列方式回傳物件的所有屬性(Enumerable or not)
name = [];
console.log(Object.getPrototypeOf(new Polygon1()))
for(let n of Object.getOwnPropertyNames(Object.getPrototypeOf(new Polygon1()))){
	name.push(n);
}
console.log(name)
//如果把Polygon1改成Polygon2，會發現只有sayName而已