前后端高效率实现Base64编码解码

// 引入 base64.js

<script type="text/javascript" src="js/base64.js"></script>

//base64.js 文件内容

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;  

    }  

}

// 用法：先实例化

var base = new Base64();

// 加密

var xxx = base.encode(xxx);

// 解密

var xxx = base.decode(xxx);