const obj={
    fullName:'zz',
    sayName(){
        console.log(`this.fullName`,this.fullName)//zz
    }
 }

 obj.sayName();

const obj={
    fullName:'zz',
    sayName:()=>{
        console.log(`this.fullName`,this.fullName)//undefined
    }
 }

 obj.sayName();

function sayName(){
    console.log(`this.fullName`,this.fullName)
}

const obj={
    fullName:'freemen'
}
sayName.call(obj);//this.fullName freemen

const sayName=(...args)=>{
    console.log(`args`,args)
}
sayName('a','b');//['a', 'b']

function Person(){
  this.name='cai';
  const target=new.target;
  console.log(`target`,target)
}
const obj=new Person;
console.log(`obj`,obj);

//箭头函数不允许使用new.target

const Person=()=>{
  this.name='cai';
  const target=new.target;
  console.log(`target`,target)
}
const obj=new Person;
console.log(`obj`,obj);//Uncaught SyntaxError: new.target expression is not allowed here

const array=[1,2,3,4,2,1,2];
//const result=new Set(array);//输出的结果是对象我们使用Array.from方法转化为数组

const result=Array.from(new Set(array));
console.log(result);//[ 1, 2, 3, 4 ]