JS 实现Base64编码与解码实例详解

//1.加密 var str = '124中文内容'; var base = new Base64(); var result = base.encode(str); //document.write(result); //2.解密 var result2 = base.decode(result); document.write(result2); 

/** * * Base64 encode / decode * * @author haitao.tu * @date 2010-04-26 * @email tuhaitao@foxmail.com * */ 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;  } }