var a = 1; //fn3之后 a = 200function fn(){    console.log(a); //un    var a = 5;    console.log(a); //5    a++; //6    var a; //6    fn3();  //1    fn2();  // 6    console.log(a); //20    function fn2(){        console.log(a)        a = 20;    }}function fn3(){    console.log(a)    a = 200;}fn();console.log(a); //200