//1.加密解密方法使用：//1.加密 var str = '124中文內容'; 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、解密算法封裝：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;   } }