javascript utf-8，unicode(utf-16)编码互换

    //javascript将UTF-16字符串转转换为UTF-8字符串
    function utf16ToUtf8(s){  
        if(!s){  
            return;  
        }  
          
        var i, code, ret = [], len = s.length;  
        for(i = 0; i < len; i++){  
            code = s.charCodeAt(i);  
            if(code > 0x0 && code <= 0x7f){  
                //单字节  
                //UTF-16 0000 - 007F  
                //UTF-8  0xxxxxxx  
                ret.push(s.charAt(i));  
            }else if(code >= 0x80 && code <= 0x7ff){  
                //双字节  
                //UTF-16 0080 - 07FF  
                //UTF-8  110xxxxx 10xxxxxx  
                ret.push(  
                    //110xxxxx  
                    String.fromCharCode(0xc0 | ((code >> 6) & 0x1f)),  
                    //10xxxxxx  
                    String.fromCharCode(0x80 | (code & 0x3f))  
                );  
            }else if(code >= 0x800 && code <= 0xffff){  
                //三字节  
                //UTF-16 0800 - FFFF  
                //UTF-8  1110xxxx 10xxxxxx 10xxxxxx  
                ret.push(  
                    //1110xxxx  
                    String.fromCharCode(0xe0 | ((code >> 12) & 0xf)),  
                    //10xxxxxx  
                    String.fromCharCode(0x80 | ((code >> 6) & 0x3f)),  
                    //10xxxxxx  
                    String.fromCharCode(0x80 | (code & 0x3f))  
                );  
            }  
        }  
          
        return ret.join('');  
    }  
    //javascript将UTF-8字符串转换为UTF-16字符串
    function utf8ToUtf16(s){  
        if(!s){  
            return;  
        }  
          
        var i, codes, bytes, ret = [], len = s.length;  
        for(i = 0; i < len; i++){  
            codes = [];  
            codes.push(s.charCodeAt(i));  
            if(((codes[0] >> 7) & 0xff) == 0x0){  
                //单字节  0xxxxxxx  
                ret.push(s.charAt(i));  
            }else if(((codes[0] >> 5) & 0xff) == 0x6){  
                //双字节  110xxxxx 10xxxxxx  
                codes.push(s.charCodeAt(++i));  
                bytes = [];  
                bytes.push(codes[0] & 0x1f);  
                bytes.push(codes[1] & 0x3f);  
                ret.push(String.fromCharCode((bytes[0] << 6) | bytes[1]));  
            }else if(((codes[0] >> 4) & 0xff) == 0xe){  
                //三字节  1110xxxx 10xxxxxx 10xxxxxx  
                codes.push(s.charCodeAt(++i));  
                codes.push(s.charCodeAt(++i));  
                bytes = [];  
                bytes.push((codes[0] << 4) | ((codes[1] >> 2) & 0xf));  
                bytes.push(((codes[1] & 0x3) << 6) | (codes[2] & 0x3f));            
                ret.push(String.fromCharCode((bytes[0] << 8) | bytes[1]));  
            }  
        }  
        return ret.join('');  
    }