练习题

        var a = 2 // 4 => 8
        var obj = {
            a :4, // 8
            fn1:(function(){
             this.a *= 2
             var a = 3 // 9 => 27
             return function(){
                 this.a *= 2
                 a*= 3
                 console.log(a); // 9
             }
            })()
        }
        var fn1 = obj.fn1
        console.log(a); // 4
        fn1() // 9
        obj.fn1() // 27
        console.log(a); // 8
        console.log(obj.a); // 8

        arr = []
        for (var index = 0; index < 3; index++) {
            arr[index] = function(){
                console.log(index);
            }
        }
    }
    fun()
    arr[0]()
    arr[1]()
    arr[2]()
    
    
    function fn() {
            var arr = []
            for (let i = 0; i < 5; i++) {
                arr[i] = function () {
                    return i
                }
            }
            return arr
        }
        var list = fn()
        console.log(list);
        for (var i = 0; len = list.length, i < len; i++) {
            console.log(list[i]());
        }