本文实例讲述了JS实现对中文字符串进行utf-8的Base64编码的方法。分享给大家供大家参考，具体如下：
要进行编码的字符串：“select 用户名 from 用户”
使用JAVA进行编码，Java程序：
String sql = "select 用户名 from 用户";String encodeStr = new String(Base64.encode(sql.getBytes("UTF-8"))); // 编码System.out.println(encodeStr);得到：
c2VsZWN0IOeUqOaIt+WQjSBmcm9tIOeUqOaItw==
在Java中解码：
sql = new String(Base64.decode(sql.getBytes()), "UTF-8");
Java代码中为什么要使用getBytes("UTF-8")呢？因为Windows和Linux环境下默认编码不同，要使你的程序在不同平台下得到相同编码，必然要指定编码
虽然Html和JS的编码都是utf-8，但JS从页面上得到的中文编码却是utf-16，所以直接对中文进行Base64编码将得到错误的结果，所以我们要先从utf-16转到utf-8再编码
<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN""http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd"><html xmlns="http://www.w3.org/1999/xhtml"><head><title></title><meta http-equiv="Content-Type" content="text/html; charset=utf-8" /><style type="text/css"><!--body{ margin:0px; padding:0px;}body,td{ font-size:9pt;}--></style><script type="text/JavaScript"><!--var keyStr = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/=";//将Ansi编码的字符串进行Base64编码function encode64(input) {var output = "";var chr1, chr2, chr3 = "";var enc1, enc2, enc3, enc4 = "";var i = 0;do {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);chr1 = chr2 = chr3 = "";enc1 = enc2 = enc3 = enc4 = "";} while (i < input.length);return output;}//将Base64编码字符串转换成Ansi编码的字符串function decode64(input) {var output = "";var chr1, chr2, chr3 = "";var enc1, enc2, enc3, enc4 = "";var i = 0;if (input.length % 4 != 0) {return "";}var base64test = /[^A-Za-z0-9/+///=]/g;if (base64test.exec(input)) {return "";}do {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 += String.fromCharCode(chr2);}if (enc4 != 64) {output += String.fromCharCode(chr3);}chr1 = chr2 = chr3 = "";enc1 = enc2 = enc3 = enc4 = "";} while (i < input.length);return output;}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;}// 测试代码 开始var de = encode64(utf16to8("select 用户名 from 用户"));document.writeln(de+"<br>");var ee = utf8to16(decode64(de))document.writeln(ee);// 测试代码 结束//--></script></head><body></body></html>上面的代码都是从网上得来，拼凑后得到正确结果，在此感谢前辈们
PS：这里再为大家推荐几款base64编码解码在线工具，相信在以后的开发中会用得到：
BASE64编码解码工具：
http://tools.VeVB.COm/transcoding/base64
在线图片转换BASE64工具：
http://tools.VeVB.COm/transcoding/img2base64
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希望本文所述对大家JavaScript程序设计有所帮助。