Javascript Base64编码和解码

/**
*
*  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(/\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;
        }
 
}