【转】Javascript Base64编码与解码

< html > < head > < META HTTP-EQUIV ="MSThemeCompatible" CONTENT ="Yes"> < meta http-equiv ="Content-Type" content ="text/html; charset=unicode"> < script language ="JavaScript" type ="text/javascript" src ="../var.js"></ script > < title > Base64 Encode and Decode </ title > < style > </ style > < script type ="text/javascript" language ="javascript"> var base64EncodeChars = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/" ; var base64DecodeChars = new Array( -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, 62, -1, -1, -1, 63, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, -1, -1, -1, -1, -1, -1, -1, 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, -1, -1, -1, -1, -1, -1, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, -1, -1, -1, -1, -1); function base64encode(str) { var out, i, len; var c1, c2, c3; len = str.length; i = 0; out = "" ; while (i < len) { c1 = str.charCodeAt(i++) & 0xff; if (i == len) { out += base64EncodeChars.charAt(c1 >> 2); out += base64EncodeChars.charAt((c1 & 0x3) << 4); out += "==" ; break ; } c2 = str.charCodeAt(i++); if (i == len) { out += base64EncodeChars.charAt(c1 >> 2); out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4)); out += base64EncodeChars.charAt((c2 & 0xF) << 2); out += "=" ; break ; } c3 = str.charCodeAt(i++); out += base64EncodeChars.charAt(c1 >> 2); out += base64EncodeChars.charAt(((c1 & 0x3)<< 4) | ((c2 & 0xF0) >> 4)); out += base64EncodeChars.charAt(((c2 & 0xF) << 2) | ((c3 & 0xC0) >>6)); out += base64EncodeChars.charAt(c3 & 0x3F); } return out; } function base64decode(str) { var c1, c2, c3, c4; var i, len, out; len = str.length; i = 0; out = "" ; while (i < len) { /* c1 */ do { c1 = base64DecodeChars[str.charCodeAt(i++) & 0xff]; } while (i < len && c1 == -1); if (c1 == -1) break ; /* c2 */ do { c2 = base64DecodeChars[str.charCodeAt(i++) & 0xff]; } while (i < len && c2 == -1); if (c2 == -1) break ; out += String.fromCharCode((c1 << 2) | ((c2 & 0x30) >> 4)); /* c3 */ do { c3 = str.charCodeAt(i++) & 0xff; if (c3 == 61) return out; c3 = base64DecodeChars[c3]; } while (i < len && c3 == -1); if (c3 == -1) break ; out += String.fromCharCode(((c2 & 0XF) << 4) | ((c3 & 0x3C) >> 2)); /* c4 */ do { c4 = str.charCodeAt(i++) & 0xff; if (c4 == 61) return out; c4 = base64DecodeChars[c4]; } while (i < len && c4 == -1); if (c4 == -1) break ; out += String.fromCharCode(((c3 & 0x03) << 6) | c4); } return out; } function utf16to8(str) { var out, i, len, c; out = "" ; len = str.length; for (i = 0; i < len; i++) { c = str.charCodeAt(i); if ((c >= 0x0001) && (c <= 0x007F)) { out += str.charAt(i); } else if (c > 0x07FF) { out += String.fromCharCode(0xE0 | ((c >> 12) & 0x0F)); out += String.fromCharCode(0x80 | ((c >> 6) & 0x3F)); out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F)); } else { out += String.fromCharCode(0xC0 | ((c >> 6) & 0x1F)); out += String.fromCharCode(0x80 | ((c >> 0) & 0x3F)); } } return out; } function utf8to16(str) { var out, i, len, c; var char2, char3; out = "" ; len = str.length; i = 0; while (i < len) { c = str.charCodeAt(i++); switch (c >> 4) { case 0: case 1: case 2: case 3: case 4: case 5: case 6: case 7: // 0xxxxxxx out += str.charAt(i-1); break ; case 12: case 13: // 110x xxxx 10xx xxxx char2 = str.charCodeAt(i++); out += String.fromCharCode(((c & 0x1F) << 6) | (char2 & 0x3F)); break ; case 14: // 1110 xxxx 10xx xxxx 10xx xxxx char2 = str.charCodeAt(i++); char3 = str.charCodeAt(i++); out += String.fromCharCode(((c & 0x0F) << 12) | ((char2 & 0x3F) << 6) | ((char3 & 0x3F) << 0)); break ; } } return out; } function CharToHex(str) { var out, i, len, c, h; out = "" ; len = str.length; i = 0; while (i < len) { c = str.charCodeAt(i++); h = c.toString(16); if (h.length < 2) h = "0" + h; out += "\\x" + h + " " ; if (i > 0 && i % 8 == 0) out += "\r\n" ; } return out; } function doEncode() { var src = document.getElementById( 'src' ).value; document.getElementById( 'dest' ).value = base64encode(utf16to8(src)); } function doDecode() { var src = document.getElementById( 'src' ).value; var opts = document.getElementById( 'opt' ); if (opts.checked) { document.getElementById( 'dest' ).value = CharToHex(base64decode(src)); } else { document.getElementById( 'dest' ).value = utf8to16(base64decode(src)); } } </ script > </ head > < BODY bgcolor ="#EAF0F8" topmargin ="10" leftmargin ="10" rightmargin ="10" bottommargin ="10"> < div id ="contain" style =" font-family : Tahoma , Arial ; font-size : 11pt"> < div id ="mainbg"> < div style =" color : #000080 ; margin-bottom : 10">< b > Base64 Encode / Decode </ b ></ div > < div > < textarea id ="src" rows =11 cols =60 value ="" name ="src"></ textarea > < div style =" margin : 10 0 10 0"> < input onclick =" doEncode(); " type =button value ="Encode" name ="encode"> &nbsp; < input onclick =" doDecode(); " type =button value ="Decode" name ="decode"> &nbsp; < input type ="checkbox" value ="hex" name ="opt" id ="opt"> Hex &nbsp; </ div > < textarea id ="dest" rows =11 cols =60 value ="" name ="dest"></ textarea > </ div > </ div > </ div > </ BODY > </ html > 本文转自齐师傅博客园博客，原文链接：http://www.cnblogs.com/youring2/archive/2013/03/04/2942880.html，如需转载请自行联系原作者