分享一个JS的Base64加密解密功能

代码实现：

---

 var base64 = (function () {
     var encodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
     var decodeChars = new Array(
                 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
                 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,
                 -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63,
                 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1,
                 -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14,
                 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1,
                 -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40,
                 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1);
     //编码
     function encode(str) {
         var out, i, len;
         var c1, c2, c3;
         len = str.length;
         i = 0;
         out = "";
         while (i < len) {
             c1 = str.charCodeAt(i++) & 0xff;
             if (i == len) {
                 out += base64.encodeChars.charAt(c1 >> 2);
                 out += base64.encodeChars.charAt((c1 & 0x3) << 4);
                 out += "==";
                 break;
             }
             c2 = str.charCodeAt(i++);
             if (i == len) {
                 out += base64.encodeChars.charAt(c1 >> 2);
                 out += base64.encodeChars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));
                 out += base64.encodeChars.charAt((c2 & 0xF) << 2);
                 out += "=";
                 break;
             }
             c3 = str.charCodeAt(i++);
             out += base64.encodeChars.charAt(c1 >> 2);
             out += base64.encodeChars.charAt(((c1 & 0x3) << 4) | ((c2 & 0xF0) >> 4));
             out += base64.encodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >> 6));
             out += base64.encodeChars.charAt(c3 & 0x3F);
         }
         return out;
     };
     //解码
     function decode(str) {
         var c1, c2, c3, c4;
         var i, len, out;
         len = str.length;
         i = 0;
         out = "";
         while (i < len) {
             /* c1 */
             do {
                 c1 = base64.decodeChars[str.charCodeAt(i++) & 0xff];
             } while (i < len && c1 == -1);
             if (c1 == -1)
                 break;
             /* c2 */
             do {
                 c2 = base64.decodeChars[str.charCodeAt(i++) & 0xff];
             } while (i < len && c2 == -1);
             if (c2 == -1)
                 break;
             out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4));
             /* c3 */
             do {
                 c3 = str.charCodeAt(i++) & 0xff;
                 if (c3 == 61)
                     return out;
                 c3 = base64.decodeChars[c3];
             } while (i < len && c3 == -1);
             if (c3 == -1)
                 break;
             out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2));
             /* c4 */
             do {
                 c4 = str.charCodeAt(i++) & 0xff;
                 if (c4 == 61)
                     return out;
                 c4 = base64.decodeChars[c4];
             } while (i < len && c4 == -1);
             if (c4 == -1)
                 break;
             out += String.fromCharCode(((c3 & 0x03) << 6) | c4);
         }
         return out;
     };
     return {
         encode: encode,
         decode: decode
     };
 })();