function StringBuffer() { 
  this.__strings__ = []; 
}; 
StringBuffer.prototype.Append = function (str) { 
  this.__strings__.push(str); 
  return this; 
}; 
//格式化字符串 
StringBuffer.prototype.AppendFormat = function (str) { 
  for (var i = 1; i < arguments.length; i++) { 
    var parent = "\\{" + (i - 1) + "\\}"; 
    var reg = new RegExp(parent, "g") 
    str = str.replace(reg, arguments[i]); 
  } 
 
  this.__strings__.push(str); 
  return this; 
} 
StringBuffer.prototype.ToString = function () { 
  return this.__strings__.join(''); 
}; 
StringBuffer.prototype.clear = function () { 
  this.__strings__ = []; 
} 
StringBuffer.prototype.size = function () { 
  return this.__strings__.length; 
}

var sbHtml=new StringBuffer(); 
sbHtml.Append('hello'); 
sbHtml.Append('world'); 
   
console.log(sbHtml.ToString());