<script>
//es6如何定义变量，定义变量特点
// js定义：var a = 1;
// es6写法定义变量，使用关键字 let let a = 10;
//let定义变量有作用范围
//1 创建代码块，定义变量
{
var a = 10
let b = 20
}
//2在代码块 外面输出
console.log(a)
console.log(b) //Uncaught ReferenceError: b is not defined
</script>
<script>
var a = 1
var a = 2
let m = 10
let m = 20 //Uncaught SyntaxError: Identifier 'm' has already been declared
console.log(a)
console.log(m)
</script>
<script>
//定义常量
const PI = "3.1415"
//常量值一旦定义，不能改变
//PI = 3 //Uncaught TypeError: Assignment to constant variable.
//定义常量必须初始化
const AA //Uncaught SyntaxError: Missing initializer in const declaration
</script>
<script>
//传统写法
let a=1,b=2,c=3
console.log(a, b, c)
//es6写法
let [x,y,z] = [10,20,30]
console.log(x, y, z)
</script>
<script>
//定义对象
let user = {"name":"lucy","age":20}
//传统从对象里面获取值
let name1 = user.name
let age1 = user.age
console.log(name1+"=="+age1)
//es6获取对象值
let {name,age} = user
console.log(name+"**"+age)
</script>
<script>
//1 使用`符号实现换行
let str1 = `hello,
es6 demo up!`
console.log(str1)
//2 在`符号里面使用表达式获取变量值
let name = "Mike"
let age = 20
let str2 = `hello,${name},age is ${age+1}`
console.log(str2)
//3 在`符号调用方法
function f1() {
return "hello f1"
}
let str3 = `demo, ${f1()}`
console.log(str3)
</script>
<script>
const age = 12
const name = "lucy"
//传统方式定义对象
const p1 = {name:name,age:age}
console.log(p1)
//es6定义变量
const p2 = {name,age}
console.log(p2)
</script>
<script>
//传统方式定义的方法
const person1 = {
sayHi:function(){
console.log("Hi")
}
}
//调用
person1.sayHi()
//es6
const person2 = {
sayHi(){
console.log("Hi")
}
}
</script>
<script>
//1 对象复制
let person1 = {"name":"lucy","age":20}
let person2 = {...person1}
//console.log(person2) //Uncaught SyntaxError: Unexpected token ...
//2 对象合并
let name = {name:'mary'}
let age = {age:30}
let p2 = {...name,...age}
console.log(p2)
</script>
<script>
//1 传统方式创建方法
//参数 => 函数体
var f1 = function(m) {
return m
}
//console.log(f1(2))
//使用箭头函数改造
var f2 = m => m
// console.log(f2(8))
//2 复杂一点方法
var f3 = function(a,b) {
return a+b
}
//console.log(f3(1,2))
//箭头函数简化
var f4 = (a,b) => a+b
console.log(f4(2,2))
</script>