第7题 下面输出什么

    var length = 10
    
    function fn(){
        console.log(this.length)
    }
    var obj = {
      length:5,
      method:function(fn){
        fn()
        arguments[0]()
        console.log(arguments,'arguments')
      }
    }
    
    obj.method(fn) // 10 1
    obj.method(fn, 123) // 10 2

    var a = {n:1}
    var b = a 
    a = {n:2}
    a.x = a 
    console.log(a.x) // {n:2, x:{n:2,x:{n:2}}}