//ES5
if (true) {
    var i = 1;
}
console.log(i);

//ES6
if (true) {
    let i = 1;
}
console.log(i)

var i = 0;
switch (i) {
    case 0:
        let value = "hello";
    case 1:
        let value = "world";
}

const data = 10;
console.log(data);
//data = 100 //执行错误

const list = [10, 20, 30];
console.log(list);

list[0] = 100;
console.log(list);

list = [1, 2, 3];//错误

list = [1, 2, 3];//list等于一个新数组，变的是list变量，当然与const定义矛盾

const list = [10, 20, 30];
console.log(list);

list.push(99);
console.log(list);

console.log(0b10);//2
console.log(0o10);//8
console.log(0x10);//16

console.log(0b11 === 3);//true
console.log(0o10 === 8);//true
console.log(0x10 === 16);//true

let num = 10;
console.log(num.toString(8));//8进制转化
console.log(num.toString(2));
console.log(num.toString(16));
console.log(num.toString(5));

let name = "fmujie"
let mystr1 = "Hello, ${ name }!"
let mystr2 = `Hello, ${ name }! 再见。`

console.log(mystr1)
console.log(mystr2)

function tagged(formats, ...args) {
    console.log(formats);
    console.log(args);
}

tagged` 你好，${ name }! 再见。` //反单引号

let name = "fmujie"
let address = "公园"
let str = `你好，${ name }! 晚上一起去${ address }玩吧!`
console.log(str)
let fmtstr = markdown`你好，${ name }! 晚上一起去${ address }玩吧!`
console.log(fmtstr)

function markdown(formats, ...args) {
    console.log(formats)
    console.log(args)
    var result = "# 信息标题\n";
    for(var i = 0; i< formats.length; i++) {
        result += formats[i] + "**" + (args[i] || '') + "**"
    }
    return result
}

let str1 = "Hello World!"
let str2 = "Hello World!"
console.log(str1 == str2)//true
console.log(str1 === str2)//true

let str3 = Symbol("MySymbol")
let str4 = Symbol("Mysymbol")
console.log(typeof str3)
console.log(str3.toString())
console.log(str3 == str4)//false
console.log(str3 === str4)//false

const Java = Symbol()
const PHP  = Symbol()

var lang = PHP

if(lang === PHP) {
    console.log("PHP")
}

let str1 = Symbol("mySymbol")
let str2 = Symbol("mySymbol")

var obj = {}
obj[str1] = "Hello"
obj[str2] = "World"

console.log(obj)
console.log(obj[str1])
console.log(obj[str2])

const MyKey = Symbol()
class User {
    constructor(key, name, age) {
        this[MyKey] = key
        this.name = name
        this.age = age
    }

    checkKey(key) {
        return this[MyKey] == key;
    }
}

let user = new User(123, 'fmujie', 18)
console.log(user.name, user.age, user[MyKey])
console.log(user.checkKey(123))
console.log(user.checkKey(456))
console.log(Object.keys(user))
console.log(JSON.stringify(user))