js模拟实现Array的sort方法

<script type="text/javascript">  
 <!--  
  var myarray = new Array(8,6,7,9,1,-1,4);  
  var myarray1 = new Array(8,6,7,9,1,-1,4);  
  var sortAsc = function(x,y) { return x-y; };  
  var sortDesc = function(x,y) { return y-x; };  
  Array.prototype.st=function(fn){  
    var t;  
    fn=fn||function(x,y){return x-y};  
    for(var i=0;i<this.length;i++){  
      for(var j=i;j<this.length;j++){  
        if(fn(this[i],this[j])>0){  
          t=this[i];  
          this[i]=this[j];  
          this[j]=t;  
        }  
      }  
    }  
  }  
  myarray.st();  
  alert("默认升序排列："+myarray);  

  myarray.st(sortDesc);  
  alert("降序排列："+myarray);  

  myarray.st(sortAsc);  
  alert("升序排列："+myarray);  
    
  myarray1.sort(function(){return 1}); //注：js默认的sort对此排序结果跟这个不一样，其排序方式还暂不理解  
  alert("逆序排列："+myarray1);    
    
 //-->  
 </script>