常量与变量 let与const:都不能重复声明;都存在块级作用域问题;只在声明所在的块级作用域内有效。而var是全局作用域。声明变量leta1声明常量constb1箭头函数js函数functiongetUser(){return{name:jack,age:18}}箭头函数constgetUser(){return{name:jack,age:18}}模板字符串字符串拼接letnamejackconsole。log(hello{name})hellojack字符串换行hellojack解构赋值constuser{name:jack,age:18,address:中国}const{name}userconsole。log(name)jack对象扩展 用于取出参数对象的所有可遍历属性,拷贝到当前对象中constuser{name:jack,age:18,address:中国}constuser2{。。。user}console。log(user2){name:jack,age:18,address:中国‘}’