轉換特殊符號，防止用戶在文本域中輸入html標籤

<span style="font-size:18px;">String.prototype.htmlEncode=function(){
    return this.replace(/&/g,"&").replace(/</g,"<").replace(/>/g,">").replace(/\"/g,""").replace(/\'/g,"'");
}
 String.prototype.htmlDecode=function(){
    return this.replace(/\&\;/g, '\&').replace(/\>\;/g, '\>').replace(/\<\;/g, '\<').replace(/\"\;/g, '\'').replace(/\&\#39\;/g, '\'');
}</span>