JS 实现Base64编码与解码实例详解

宽为限 紧用功 功工夫到 滞塞通

Js实现Base64编码与解码

Base64其实是一种简单的置换加密方式，但是BASE64的用处往往并不是为了防止信息泄露，而且为了方便传输，进过BASE64编码后的信息会比原始信息长，大概是4/3倍。

Base64是一种基于64个可打印字符来表示二进制数据的表示方法。由于2的6次方等于64，所以每6个比特为一个单元，对应某个可打印字符。
Base64常用于在通常处理文本数据的场合，表示、传输、存储一些二进制数据。包括MIME的email，email via MIME, 在XML中存储复杂数据。

1.加密解密方法使用：

//1.加密 
var str = '124中文内容'; 
var base = new Base64(); 
var result = base.encode(str); 
//document.write(result); 
//2.解密 
var result2 = base.decode(result); 
document.write(result2); 

2.加密、解密算法封装：

   /**
    *
    * Base64 encode / decode
    * @author haitao.tu
    * @date   2010-04-26
    * @email  tuhaitao@foxmail.com
    *
    **/
    function Base64() {  

       // private property  
       _keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";  

       // public method for encoding  
       this.encode = function (input) {  
           var output = "";  
           var chr1, chr2, chr3, enc1, enc2, enc3, enc4;  
           var i = 0;  
           input = _utf8_encode(input);  
           while (i < input.length) {  
               chr1 = input.charCodeAt(i++);  
               chr2 = input.charCodeAt(i++);  
               chr3 = input.charCodeAt(i++);  
               enc1 = chr1 >> 2;  
               enc2 = ((chr1 & 3) << 4) | (chr2 >> 4);  
               enc3 = ((chr2 & 15) << 2) | (chr3 >> 6);  
               enc4 = chr3 & 63;  
               if (isNaN(chr2)) {  
                   enc3 = enc4 = 64;  
               } else if (isNaN(chr3)) {  
                   enc4 = 64;  
               }  
               output = output +  
               _keyStr.charAt(enc1) + _keyStr.charAt(enc2) +  
               _keyStr.charAt(enc3) + _keyStr.charAt(enc4);  
           }  
           return output;  
       }  

       // public method for decoding  
       this.decode = function (input) {  
           var output = "";  
           var chr1, chr2, chr3;  
           var enc1, enc2, enc3, enc4;  
           var i = 0;  
           input = input.replace(/[^A-Za-z0-9\+\/\=]/g, "");  
           while (i < input.length) {  
               enc1 = _keyStr.indexOf(input.charAt(i++));  
               enc2 = _keyStr.indexOf(input.charAt(i++));  
               enc3 = _keyStr.indexOf(input.charAt(i++));  
               enc4 = _keyStr.indexOf(input.charAt(i++));  
               chr1 = (enc1 << 2) | (enc2 >> 4);  
               chr2 = ((enc2 & 15) << 4) | (enc3 >> 2);  
               chr3 = ((enc3 & 3) << 6) | enc4;  
               output = output + String.fromCharCode(chr1);  
               if (enc3 != 64) {  
                   output = output + String.fromCharCode(chr2);  
               }  
               if (enc4 != 64) {  
                   output = output + String.fromCharCode(chr3);  
               }  
           }  
           output = _utf8_decode(output);  
           return output;  
       }  

       // private method for UTF-8 encoding  
       _utf8_encode = function (string) {  
           string = string.replace(/\r\n/g,"\n");  
           var utftext = "";  
           for (var n = 0; n < string.length; n++) {  
               var c = string.charCodeAt(n);  
               if (c < 128) {  
                   utftext += String.fromCharCode(c);  
               } else if((c > 127) && (c < 2048)) {  
                   utftext += String.fromCharCode((c >> 6) | 192);  
                   utftext += String.fromCharCode((c & 63) | 128);  
               } else {  
                   utftext += String.fromCharCode((c >> 12) | 224);  
                   utftext += String.fromCharCode(((c >> 6) & 63) | 128);  
                   utftext += String.fromCharCode((c & 63) | 128);  
               }  

           }  
           return utftext;  
       }  

       // private method for UTF-8 decoding  
       _utf8_decode = function (utftext) {  
           var string = "";  
           var i = 0;  
           var c = c1 = c2 = 0;  
           while ( i < utftext.length ) {  
               c = utftext.charCodeAt(i);  
               if (c < 128) {  
                   string += String.fromCharCode(c);  
                   i++;  
               } else if((c > 191) && (c < 224)) {  
                   c2 = utftext.charCodeAt(i+1);  
                   string += String.fromCharCode(((c & 31) << 6) | (c2 & 63));  
                   i += 2;  
               } else {  
                   c2 = utftext.charCodeAt(i+1);  
                   c3 = utftext.charCodeAt(i+2);  
                   string += String.fromCharCode(((c & 15) << 12) | ((c2 & 63) << 6) | (c3 & 63));  
                   i += 3;  
               }  
           }  
           return string;  
       }  
    }  

站在巨人的肩膀上

本篇博文转载的地址
http://www.jb51.net/article/96720.htm