Array.prototype.sort=function()
  {
      var tmp;
      for(var i=0;i<this.length;i++)
      {
          for(var j=0;j<this.length;j++)
          {
              if(this[i]<this[j])
              {
                  tmp = this[i];
                  this[i] = this[j];
                  this[j] = tmp;
              }
          }
      }
  };
  
  Array.prototype.unshift=function(item)
  {
      this[this.length] = null;/* create a new last element */
      for(var i=1;i<this.length;i++)
      {
          this[i] = this[i-1]; /* shift elements upwards */
      }
      this[0] = item;
  };
  
/*  Array.prototype.shift=function()
  {
      for(var i=1;i<this.length;i++)
      {
          this[i-1] = this[i] 
      }
      this.length =  this.length-1;
  };
*/
  
  Array.prototype.clear=function()
  {
      this.length = 0;
  };
  
  Array.prototype.contains = function (element) 
  {
          for (var i = 0; i < this.length; i++) 
       {
              if (this[i] == element) 
          {
                      return true;
              }
          }
          return false;
  };
  
/* Shuffles the Array elements randomly */  
Array.prototype.shuffle = function()
{
    var i=this.length,j,t;      
    while(i--)      
    {          
        j=Math.floor((i+1)*Math.random());          
        t=arr[i];          
        arr[i]=arr[j];          
        arr[j]=t;      
    }  
}    

/* Removes redundant elements from the array */  
Array.prototype.unique=function()  
{      
    var a=[],i;      
    this.sort();      
    for(i=0;i<this.length;i++)      
    {          
        if(this[i]!==this[i+1])          
        {              
            a[a.length]=this[i];          
        }      
    }      
    return a;  
}    

/* Returns the index of the element matched from the behind */  
Array.prototype.lastIndexOf=function(n)  
{      
    var i=this.length;      
    while(i--)      
    {          
        if(this[i]===n)          
        {              
            return i;          
        }      
    }      
    return -1;  
}