Base16编码的ECMAScript语言实现如下：

//ECMAScript中的字符串采用UTF16编码的
//我们先获得每个字符的codePoint，然后再转换为UTF8编码，最后把每个字节转成ASCII编码
function codePoint2UTF8(str) {
    var strLength = str.length;
    var utf8Bytes = [];
    for (var i = 0; i < strLength; i++) {
        var code = str.charCodeAt(i);
        if (code > 0x0000 && code <= 0x007F) {
            // 单字节，这里并不考虑0x0000，因为它是空字节
            // U+00000000 – U+0000007F     0xxxxxxx
            utf8Bytes.push(str.charAt(i));
        } else if (code >= 0x0080 && code <= 0x07FF) {
            // 双字节
            // U+00000080 – U+000007FF     110xxxxx 10xxxxxx
            // 110xxxxx
            var byte1 = 0xC0 | ((code >> 6) & 0x1F);
            // 10xxxxxx
            var byte2 = 0x80 | (code & 0x3F);
            utf8Bytes.push(
                String.fromCharCode(byte1),
                String.fromCharCode(byte2)
            );
        } else if (code >= 0x0800 && code <= 0xFFFF) {
            // 三字节
            // U+00000800 – U+0000FFFF     1110xxxx 10xxxxxx 10xxxxxx
            // 1110xxxx
            var byte1 = 0xE0 | ((code >> 12) & 0x0F);
            // 10xxxxxx
            var byte2 = 0x80 | ((code >> 6) & 0x3F);
            // 10xxxxxx
            var byte3 = 0x80 | (code & 0x3F);
            utf8Bytes.push(
                String.fromCharCode(byte1),
                String.fromCharCode(byte2),
                String.fromCharCode(byte3)
            );
        } else if (code >= 0x00010000 && code <= 0x001FFFFF) {
            // 四字节
            // U+00010000 – U+001FFFFF     11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
        } else if (code >= 0x00200000 && code <= 0x03FFFFFF) {
            // 五字节
            // U+00200000 – U+03FFFFFF     111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
        } else /** if (code >= 0x04000000 && code <= 0x7FFFFFFF)*/ {
            // 六字节
            // U+04000000 – U+7FFFFFFF     1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
        }
    }
    return utf8Bytes.join('');
}

var base16EncodeTable = ['0', '1', '2', '3', '4', '5', '6', '7', '8', '9', 'A', 'B', 'C', 'D', 'E', 'F'];

function base16_encode(str) {
    var utf8Str = codePoint2UTF8(str);
    var base16EncodedStr = "";
    var utf8StrLength = utf8Str.length;
    for (var i = 0; i < utf8StrLength; i++) {
        var ascii = utf8Str.charCodeAt(i);
        //向右移动4bit，获得高4bit
        var highByte = ascii >> 4;
        //与0x0f做位与运算，获得低4bit
        var lowByte = ascii & 0x0F;
        base16EncodedStr = base16EncodedStr.concat(base16EncodeTable[highByte], base16EncodeTable[lowByte]);
    }
    return base16EncodedStr;
}

Base16解码的ECMAScript语言实现如下：

function ascii2UTF16(str) {
    var strLength = str.length;
    var utf16Chars = [];
    for (var i = 0; i < strLength; i++) {
        var ascii = str.charCodeAt(i);
        // 对第一个字节进行判断，看看最高1位是否为1
        if (((ascii >> 7) & 0xFF) == 0x0) {
            // 单字节
            // 0xxxxxxx
            utf16Chars.push(str.charAt(i));
        } else if (((ascii >> 5) & 0xFF) == 0x6) {
            // 双字节
            // 110xxxxx 10xxxxxx
            var code2 = str.charCodeAt(++i);
            var byte1 = (ascii & 0x1F) << 6;
            var byte2 = code2 & 0x3F;
            var utf16 = byte1 | byte2;
            utf16Chars.push(Sting.fromCharCode(utf16));
        } else if (((ascii >> 4) & 0xFF) == 0xE) {
            // 三字节
            // 1110xxxx 10xxxxxx 10xxxxxx
            var code2 = str.charCodeAt(++i);
            var code3 = str.charCodeAt(++i);
            var byte1 = (ascii << 4) | ((code2 >> 2) & 0x0F);
            var byte2 = ((code2 & 0x03) << 6) | (code3 & 0x3F);
            var utf16 = ((byte1 & 0x00FF) << 8) | byte2
            utf16Chars.push(String.fromCharCode(utf16));
        } else if (((ascii >> 3) & 0xFF) == 0x1E) {
            // 四字节
            // 11110xxx 10xxxxxx 10xxxxxx 10xxxxxx
        } else if (((ascii >> 2) & 0xFF) == 0x3E) {
            // 五字节
            // 111110xx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
        } else /** if (((ascii >> 1) & 0xFF) == 0x7E)*/ {
            // 六字节
            // 1111110x 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx 10xxxxxx
        }
    }
    return utf16Chars.join('');
}

//把16进制字符转换成10进制表示的数字
//man ascii查看ascii对应表
//字符   十进制
//'0' => 48
//'9' => 57
//'a' => 97
//'f' => 102
//'A' => 65
//'F' => 70
function hex2dec(asciiCode) {
    if (48 <= asciiCode && asciiCode <= 57) {
        return asciiCode - 48;
    } else if (97 <= asciiCode && asciiCode <= 102) {
        return asciiCode - 97 + 10;
    } else if (65 <= asciiCode && asciiCode <= 70) {
        return asciiCode - 65 + 10;
    } else {
        return 0;
    }
}

function base16_decode(str) {
    var strLength = str.length;
    var halfStrLength = strLength / 2;
    var asciiChars = [];
    for (var i = 0; i < halfStrLength; i++) {
        var c1 = str.charCodeAt(2 * i);
        var c0 = str.charCodeAt(2 * i + 1);
        //16进制数字转换为10进制数字的过程
        var ascii = hex2dec(c1) * 16 + hex2dec(c0);
        asciiChars[i] = String.fromCharCode(ascii);
    }
    return ascii2UTF16(asciiChars.join(''));
}