JAVASCRIPT BASE64 encoding and decoding

Code:

var Base64 = {//transcoding tables table: [' A ', ' B ', ' C ', ' D ', ' E ', ' F ', ' G ', ' H ', ' I ', ' J ', ' K ', ' L ', ' M ', ' N ', ' O ', ' P '  , ' Q ', ' R ', ' S ', ' T ', ' U ', ' V ', ' W ', ' X ', ' Y ', ' Z ', ' A ', ' B ', ' C ', ' d ', ' e ', ' f ', ' g ', ' h ', ' I ', ' J ',        ' K ', ' l ', ' m ', ' n ', ' o ', ' P ', ' Q ', ' R ', ' s ', ' t ', ' u ', ' V ', ' w ', ' x ', ' y ', ' z ', ' 0 ', ' 1 ', ' 2 ', ' 3 ',    ' 4 ', ' 5 ', ' 6 ', ' 7 ', ' 8 ', ' 9 ', ' + ', '/'],utf16toutf8:function (str) {var res = [], len = str.length;        for (var i = 0; i < len; i++) {var code = str.charcodeat (i); if (Code > 0x0000 && Code <= 0x007F) {//single byte, this is not considered 0x0000, because it is empty bytes//u+00000000–u+0        000007F 0xxxxxxx Res.push (Str.charat (i)); } else if (code >= 0x0080 && Code <= 0x07ff) {//Double byte//u+00000080–u+000007ff 110x XXXX 10xxxxxx//110xxxxx var byte1 = 0xC0 |            (Code >> 6) & 0x1F); 10xxxxxx var byte2 = 0x80 |            (Code & 0x3F);        Res.push (String.fromCharCode (byte1), String.fromCharCode (Byte2)); } else if (code >= 0x0800 && Code <= 0xFFFF) {//three bytes//U+00000800–U+0000FFFF 1110 XXXX 10xxxxxx 10xxxxxx//1110xxxx var byte1 = 0xE0 |            (Code >>) & 0x0F); 10xxxxxx var byte2 = 0x80 |            (Code >> 6) & 0x3F); 10xxxxxx var byte3 = 0x80 |            (Code & 0x3F); Res.push (String.fromCharCode (byte1), String.fromCharCode (Byte2), string.fr        Omcharcode (Byte3)); } else if (code >= 0x00010000 && Code <= 0X001FFFFF) {//four bytes//U+00010000–U+001FFF            FF 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx} else if (code >= 0x00200000 && Code <= 0x03ffffff) { Five Bytes//u+00200000–U+03FFFFFF 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx} else/** if (code >= 0x04000000 && Code <= 0x7FFFFFFF) */{//Six bytes//u+04000000–u+7fffffff 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10x    XXXXX}} return Res.join (");},utf8toutf16:function (str) {var res = [], len = str.length;    var i = 0;        for (var i = 0; i < len; i++) {var code = str.charcodeat (i); The first byte is judged if (((Code >> 7) & 0xFF) = = 0x0) {//single-byte//0xxxxxxx Res.        Push (Str.charat (i));  } else if (((Code >> 5) & 0xFF) = = 0x6) {//double-byte//110xxxxx 10xxxxxx var code2            = Str.charcodeat (++i);            var byte1 = (Code & 0x1F) << 6;            var byte2 = code2 & 0x3F; var utf16 = byte1 |            Byte2;        Res.push (String.fromCharCode (UTF16)); } else if (((Code >> 4) & 0xFF) = = 0xE) {//Three bytes//1110xxxx 10xxxxxx 10xxxxxx var code2 = str.charcodeat (++i);            var code3 = str.charcodeat (++i); var byte1 = (Code << 4) |            ((Code2 >> 2) & 0x0F); var byte2 = ((Code2 & 0x03) << 6) |            (Code3 & 0x3F); var utf16 = ((Byte1 & 0x00FF) << 8) |        Byte2 Res.push (String.fromCharCode (UTF16));        } else if (((Code >> 3) & 0xFF) = = 0x1E) {//four bytes//11110xxx 10xxxxxx 10xxxxxx 10xxxxxx } else if (((Code >> 2) & 0xFF) = = 0x3e) {//Five bytes//111110xx 10xxxxxx 10xxxxxx 10xx XXXX 10xxxxxx} else/** if (((Code >> 1) & 0xFF) = = 0x7E) */{//Six bytes//1111110x 1         0xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx}} return Res.join (");},encode:function (str) {if (!STR) {    Return '; } var UTF8 = this. Utf16toutf8 (str); Turn into UTF8 var i = 0; Traverse index var len = utf8.length;    var res = [];        while (I < len) {var C1 = utf8.charcodeat (i++) & 0xFF;        Res.push (THIS.TABLE[C1 >> 2]);            Need to fill 2 = if (i = = len) {Res.push (this.table[(C1 & 0x3) << 4]);            Res.push (' = = ');        Break        } var c2 = Utf8.charcodeat (i++); Need to fill 1 = if (i = = len) {Res.push (this.table[(C1 & 0x3) << 4) |            ((C2 >> 4) & 0x0F)]);            Res.push (this.table[(C2 & 0x0F) << 2]);            Res.push (' = ');        Break        } var C3 = Utf8.charcodeat (i++); Res.push (this.table[(C1 & 0x3) << 4) |        ((C2 >> 4) & 0x0F)]); Res.push (this.table[(C2 & 0x0F) << 2) |        ((C3 & 0xC0) >> 6)]);    Res.push (THIS.TABLE[C3 & 0x3F]);    } return Res.join (");},decode:function (str) {if (!str) {return ';    } var len = str.length;    var i = 0; var res = [];        while (I < len) {code1 = This.table.indexOf (Str.charat (i++));        Code2 = This.table.indexOf (Str.charat (i++));        Code3 = This.table.indexOf (Str.charat (i++));        Code4 = This.table.indexOf (Str.charat (i++)); C1 = (code1 << 2) |        (Code2 >> 4);        Res.push (String.fromCharCode (C1)); if (code3! =-1) {C2 = ((Code2 & 0xF) << 4) |            (Code3 >> 2);        Res.push (String.fromCharCode (C2));            } if (Code4! =-1) {C3 = ((Code3 & 0x3) << 6) | Code4;        Res.push (String.fromCharCode (C3)); }} return this. Utf8toutf16 (Res.join ('));}};

Example:

var a = Base64.encode(‘小火柴‘)console.log(a)  #  输出  5bCP54Gr5p+0var b = Base64.decode(a)  console.log(b)  #  输出  小火柴

JAVASCRIPT BASE64 encoding and decoding