es6种for循环中let和var区别

 1 for(var i=0;i<5;i++){
 2    setTimeout(()=>{
 3         console.log(i);//5个5
 4     },100) 
 5 }
 6 console.log(i);//5
 7 console.log('=============')
 8 
 9 for(let j=0;j<5;j++){
10    setTimeout(()=>{
11         console.log(j);//0,1,2,3,4
12     },100) 
13 }
14 console.log(j);//报错 j is not defined;