JS中的 Base64 encode / decode 加密解密

/**

*

*  Base64 encode / decode

*  http://www.webtoolkit.info/

*

**/

 


var Base64 = {

 


    // private property


    _keyStr : "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=",

 


    // public method for encoding


    encode : function (input) {


        var output = "";


        var chr1, chr2, chr3, enc1, enc2, enc3, enc4;


        var i = 0;

 


        input = Base64._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 +


            this._keyStr.charAt(enc1) + this._keyStr.charAt(enc2) +


            this._keyStr.charAt(enc3) + this._keyStr.charAt(enc4);

 


        }

 


        return output;


    },

 


    // public method for decoding


    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 = this._keyStr.indexOf(input.charAt(i++));


            enc2 = this._keyStr.indexOf(input.charAt(i++));


            enc3 = this._keyStr.indexOf(input.charAt(i++));


            enc4 = this._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 = Base64._utf8_decode(output);

 


        return output;

 


    },

 


    // private method for UTF-8 encoding


    _utf8_encode : function (string) {


        string = string.replace(/
/g,"
");


        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;


    }

 

}