function StringBuffer()    
{    
    this._strings = [];    
    if(arguments.length==1)    
    {    
        this._strings.push(arguments[0]);    
    }    
}    
   
StringBuffer.prototype.append = function(str)    
{    
    this._strings.push(str);    
    return this;    
}    
   
StringBuffer.prototype.toString = function()    
{    
    return this._strings.join("");    
}    
     
StringBuffer.prototype.length = function()    
{    
    var str = this._strings.join("");    
    return str.length;    
}    
   
StringBuffer.prototype.del = function(num)    
{    
    var len = this.length();    
    var str = this.toString();    
    str     = str.slice(0,len-num);    
    this._strings = [];    
    this._strings.push(str);    
}

String.prototype.trim = function()
{     
    return this.replace(/(^\s*)|(\s*$)/g, "");
}

Array.prototype.del = function(n){
    return n < 0 ? this : this.slice(0, n).concat(this.slice(n + 1, this.length));
}