js 实现StringBuffer

function StringBuffer(){var buffer = [] ;// 存放字符串数组var size = 0 ;// 存放数组大小// 追加字符串this.append = function(s){if(s != null ){buffer.push(s);size++ ;} }// 返回字符串this.toString = function(){return buffer.join("");}// 清空this.clear = function(key){size = 0 ;buffer = [] ;} // 返回数组大小this.size = function(){return size ;}// 返回数组this.toArray = function(){return buffer ;}// 倒序返回字符串this.doReverse = function(){var str = buffer.join('') ; str = str.split('');  return str.reverse().join('');} }

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