es6 for循环中let和var区别详解 let和var区别: for(var i=0;i<5;i++){ setTimeout(()=>{ console.log(i);//5个5 },100) } console.log(i);//5 console.log(‘=============’) for(let j=0;j<5;j++){ setTimeout(()=>{ console.log(j);//0,1,2,3,4 },100) } console.log(j);//报错 j is not define