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     <title>Page Title</title>

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     *{font-family: Consolas;font-style: italic}

     .responsebox{width:900px;margin:10px auto;padding:10px;border:2px solid #366;border-radius: 10px 0 10px 0; text-align: center}

     .responsebox input,.responsebox button{font-size: 30px;margin:5px;padding:5px;}

     .spansuper{vertical-align: super;font-size: 14px}

     .spanbottom{vertical-align: text-bottom;font-size: 12px;margin-left: -110px}

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     <h1>Javascript Base64 Encode & Decode<span class="spansuper">veinyf@gmail.com</span><span class="spanbottom">2014-12-27 17:44</span></h1>

     <input type="text" id="input">

     <input type="checkbox" id="checkbox" checked="checked">Base64</input>

     <button id="btn">Convert done !</button>

 </div>

 <div id="showbox"></div>

 </body>

 <script type="text/javascript">

     /*javascript知識(shí)：

      *函數(shù)：window.atob()    window.btoa()   unescape() escape() encodeURIComponent() decodeURIComponent()

      *正則表達(dá)式清除首位空格：_string.replace(/(^\s*)|(\s*$)/g,"");

      *

      *CovertBase64orString自執(zhí)行函數(shù)

      *inputid   輸入框id

      *checkboxid    選擇框id

      *btnid 按鈕id

      *showid    html顯示容器id，這里是一個(gè)div#showbox

      */

 (function CovertBase64orString(inputid, checkboxid, btnid, showid) {

     var checkbox = document.getElementById(checkboxid); //html dom select checkbox

     var chkvalue = checkbox.getAttribute("checked");    //html dom select checkedvalue

     var btn = document.getElementById(btnid);           //html dom select button id

     var isbase64;                                       //base64toString or StringtoBase64 bool

     var returnval = null;                               //Converted string

     chkvalue == "checked" ? isbase64 = true : isbase64 = false; //判斷check按鈕初始化狀態(tài) 賦值isbase64

     checkbox.addEventListener("click", function(e) {            //checkbox 點(diǎn)擊事件注冊(cè)

         var _ckvak = checkbox.getAttribute("checked");          //點(diǎn)擊事件發(fā)生時(shí)，改變check狀態(tài)，賦值isbase64

         if (_ckvak == "checked") {

             checkbox.setAttribute("checked", null);

             isbase64 = false;

         } else {

             checkbox.setAttribute("checked", "checked");

             isbase64 = true;

         }

     }, true);

     btn.addEventListener("click", function(e) {                    //button 點(diǎn)擊事件注冊(cè)

         var _show = document.getElementById(showid);               //html dom select showbox id

         var _inputvalue = document.getElementById(inputid).value;   //文本框取值

         //_inputvalue=_inputvalue.replace(/(^\s*)|(\s*$)/g, "");    //正則表達(dá)式去除首位空格，似乎btoa，abob已經(jīng)做了這些工作

         var _showlength = _show.childNodes.length;                  //遍歷showbox，清除showbox內(nèi)容

         while (_showlength > 0) {

             _show.removeChild(_show.childNodes[_showlength - 1]);

             _showlength--;

         }

         if (isbase64) {  //string to base64，支持中文編碼，unescape，encodeURIComponent

             returnval = window.btoa(unescape(encodeURIComponent(_inputvalue)));

         } else {        //base64 to string

             returnval = decodeURIComponent(escape(window.atob(_inputvalue)));

         }

         _show.appendChild(document.createTextNode(returnval));          //add context to showbox

     }, true);

 })("input", "checkbox", "btn","showbox");

 //CovertBase64orString("input", "checkbox", "btn","showbox");

 </script>

 </html>