Converting punycode with dash character to Unicode

//Javascript Punycode converter derived from example in RFC3492.
//This implementation is created by some@domain.name and released into public domain
var punycode = new function Punycode() {
    // This object converts to and from puny-code used in IDN
    //
    // punycode.ToASCII ( domain )
    // 
    // Returns a puny coded representation of "domain".
    // It only converts the part of the domain name that
    // has non ASCII characters. I.e. it dosent matter if
    // you call it with a domain that already is in ASCII.
    //
    // punycode.ToUnicode (domain)
    //
    // Converts a puny-coded domain name to unicode.
    // It only converts the puny-coded parts of the domain name.
    // I.e. it dosent matter if you call it on a string
    // that already has been converted to unicode.
    //
    //
    this.utf16 = {
        // The utf16-class is necessary to convert from javascripts internal character representation to unicode and back.
        decode:function(input){
            var output = [], i=0, len=input.length,value,extra;
            while (i < len) {
                value = input.charCodeAt(i++);
                if ((value & 0xF800) === 0xD800) {
                    extra = input.charCodeAt(i++);
                    if ( ((value & 0xFC00) !== 0xD800) || ((extra & 0xFC00) !== 0xDC00) ) {
                        throw new RangeError("UTF-16(decode): Illegal UTF-16 sequence");
                    }
                    value = ((value & 0x3FF) << 10) + (extra & 0x3FF) + 0x10000;
                }
                output.push(value);
            }
            return output;
        },
        encode:function(input){
            var output = [], i=0, len=input.length,value;
            while (i < len) {
                value = input[i++];
                if ( (value & 0xF800) === 0xD800 ) {
                    throw new RangeError("UTF-16(encode): Illegal UTF-16 value");
                }
                if (value > 0xFFFF) {
                    value -= 0x10000;
                    output.push(String.fromCharCode(((value >>>10) & 0x3FF) | 0xD800));
                    value = 0xDC00 | (value & 0x3FF);
                }
                output.push(String.fromCharCode(value));
            }
            return output.join("");
        }
    }

    //Default parameters
    var initial_n = 0x80;
    var initial_bias = 72;
    var delimiter = "\x2D";
    var base = 36;
    var damp = 700;
    var tmin=1;
    var tmax=26;
    var skew=38;
    var maxint = 0x7FFFFFFF;

    // decode_digit(cp) returns the numeric value of a basic code 
    // point (for use in representing integers) in the range 0 to
    // base-1, or base if cp is does not represent a value.

    function decode_digit(cp) {
        return cp - 48 < 10 ? cp - 22 : cp - 65 < 26 ? cp - 65 : cp - 97 < 26 ? cp - 97 : base;
    }

    // encode_digit(d,flag) returns the basic code point whose value
    // (when used for representing integers) is d, which needs to be in
    // the range 0 to base-1. The lowercase form is used unless flag is
    // nonzero, in which case the uppercase form is used. The behavior
    // is undefined if flag is nonzero and digit d has no uppercase form. 

    function encode_digit(d, flag) {
        return d + 22 + 75 * (d < 26) - ((flag != 0) << 5);
        //  0..25 map to ASCII a..z or A..Z 
        // 26..35 map to ASCII 0..9
    }
    //** Bias adaptation function **
    function adapt(delta, numpoints, firsttime ) {
        var k;
        delta = firsttime ? Math.floor(delta / damp) : (delta >> 1);
        delta += Math.floor(delta / numpoints);

        for (k = 0; delta > (((base - tmin) * tmax) >> 1); k += base) {
                delta = Math.floor(delta / ( base - tmin ));
        }
        return Math.floor(k + (base - tmin + 1) * delta / (delta + skew));
    }

    // encode_basic(bcp,flag) forces a basic code point to lowercase if flag is zero,
    // uppercase if flag is nonzero, and returns the resulting code point.
    // The code point is unchanged if it is caseless.
    // The behavior is undefined if bcp is not a basic code point.

    function encode_basic(bcp, flag) {
        bcp -= (bcp - 97 < 26) << 5;
        return bcp + ((!flag && (bcp - 65 < 26)) << 5);
    }

    // Main decode
    this.decode=function(input,preserveCase) {
        // Dont use utf16
        var output=[];
        var case_flags=[];
        var input_length = input.length;

        var n, out, i, bias, basic, j, ic, oldi, w, k, digit, t, len;

        // Initialize the state: 

        n = initial_n;
        i = 0;
        bias = initial_bias;

        // Handle the basic code points: Let basic be the number of input code 
        // points before the last delimiter, or 0 if there is none, then
        // copy the first basic code points to the output.

        basic = input.lastIndexOf(delimiter);
        if (basic < 0) basic = 0;

        for (j = 0; j < basic; ++j) {
            if(preserveCase) case_flags[output.length] = ( input.charCodeAt(j) -65 < 26);
            if ( input.charCodeAt(j) >= 0x80) {
                throw new RangeError("Illegal input >= 0x80");
            }
            output.push( input.charCodeAt(j) );
        }

        // Main decoding loop: Start just after the last delimiter if any
        // basic code points were copied; start at the beginning otherwise. 

        for (ic = basic > 0 ? basic + 1 : 0; ic < input_length; ) {

            // ic is the index of the next character to be consumed,

            // Decode a generalized variable-length integer into delta,
            // which gets added to i. The overflow checking is easier
            // if we increase i as we go, then subtract off its starting 
            // value at the end to obtain delta.
            for (oldi = i, w = 1, k = base; ; k += base) {
                    if (ic >= input_length) {
                        throw RangeError ("punycode_bad_input(1)");
                    }
                    digit = decode_digit(input.charCodeAt(ic++));

                    if (digit >= base) {
                        throw RangeError("punycode_bad_input(2)");
                    }
                    if (digit > Math.floor((maxint - i) / w)) {
                        throw RangeError ("punycode_overflow(1)");
                    }
                    i += digit * w;
                    t = k <= bias ? tmin : k >= bias + tmax ? tmax : k - bias;
                    if (digit < t) { break; }
                    if (w > Math.floor(maxint / (base - t))) {
                        throw RangeError("punycode_overflow(2)");
                    }
                    w *= (base - t);
            }

            out = output.length + 1;
            bias = adapt(i - oldi, out, oldi === 0);

            // i was supposed to wrap around from out to 0,
            // incrementing n each time, so we'll fix that now: 
            if ( Math.floor(i / out) > maxint - n) {
                throw RangeError("punycode_overflow(3)");
            }
            n += Math.floor( i / out ) ;
            i %= out;

            // Insert n at position i of the output: 
            // Case of last character determines uppercase flag: 
            if (preserveCase) { case_flags.splice(i, 0, input.charCodeAt(ic -1) -65 < 26);}

            output.splice(i, 0, n);
            i++;
        }
        if (preserveCase) {
            for (i = 0, len = output.length; i < len; i++) {
                if (case_flags[i]) {
                    output[i] = (String.fromCharCode(output[i]).toUpperCase()).charCodeAt(0);
                }
            }
        }
        return this.utf16.encode(output);
    };

    //** Main encode function **

    this.encode = function (input,preserveCase) {
        //** Bias adaptation function **

        var n, delta, h, b, bias, j, m, q, k, t, ijv, case_flags;

        if (preserveCase) {
            // Preserve case, step1 of 2: Get a list of the unaltered string
            case_flags = this.utf16.decode(input);
        }
        // Converts the input in UTF-16 to Unicode
        input = this.utf16.decode(input.toLowerCase());

        var input_length = input.length; // Cache the length

        if (preserveCase) {
            // Preserve case, step2 of 2: Modify the list to true/false
            for (j=0; j < input_length; j++) {
                case_flags[j] = input[j] != case_flags[j];
            }
        }

        var output=[];


        // Initialize the state: 
        n = initial_n;
        delta = 0;
        bias = initial_bias;

        // Handle the basic code points: 
        for (j = 0; j < input_length; ++j) {
            if ( input[j] < 0x80) {
                output.push(
                    String.fromCharCode(
                        case_flags ? encode_basic(input[j], case_flags[j]) : input[j]
                    )
                );
            }
        }

        h = b = output.length;

        // h is the number of code points that have been handled, b is the
        // number of basic code points 

        if (b > 0) output.push(delimiter);

        // Main encoding loop: 
        //
        while (h < input_length) {
            // All non-basic code points < n have been
            // handled already. Find the next larger one: 

            for (m = maxint, j = 0; j < input_length; ++j) {
                ijv = input[j];
                if (ijv >= n && ijv < m) m = ijv;
            }

            // Increase delta enough to advance the decoder's
            // <n,i> state to <m,0>, but guard against overflow: 

            if (m - n > Math.floor((maxint - delta) / (h + 1))) {
                throw RangeError("punycode_overflow (1)");
            }
            delta += (m - n) * (h + 1);
            n = m;

            for (j = 0; j < input_length; ++j) {
                ijv = input[j];

                if (ijv < n ) {
                    if (++delta > maxint) return Error("punycode_overflow(2)");
                }

                if (ijv == n) {
                    // Represent delta as a generalized variable-length integer: 
                    for (q = delta, k = base; ; k += base) {
                        t = k <= bias ? tmin : k >= bias + tmax ? tmax : k - bias;
                        if (q < t) break;
                        output.push( String.fromCharCode(encode_digit(t + (q - t) % (base - t), 0)) );
                        q = Math.floor( (q - t) / (base - t) );
                    }
                    output.push( String.fromCharCode(encode_digit(q, preserveCase && case_flags[j] ? 1:0 )));
                    bias = adapt(delta, h + 1, h == b);
                    delta = 0;
                    ++h;
                }
            }

            ++delta, ++n;
        }
        return output.join("");
    }

    this.ToASCII = function ( domain ) {
        var domain_array = domain.split(".");
        var out = [];
        for (var i=0; i < domain_array.length; ++i) {
            var s = domain_array[i];
            out.push(
                s.match(/[^A-Za-z0-9-]/) ?
                "xn--" + punycode.encode(s) :
                s
            );
        }
        return out.join(".");
    }
    this.ToUnicode = function ( domain ) {
        var domain_array = domain.split(".");
        var out = [];
        for (var i=0; i < domain_array.length; ++i) {
            var s = domain_array[i];
            out.push(
                s.match(/^xn--/) ?
                punycode.decode(s.slice(4)) :
                s
            );
        }
        return out.join(".");
    }
}();


// Example of usage:
domain.oninput = function() {
    var input = domain.value
    var ascii = punycode.ToASCII(input)
    var display = punycode.ToUnicode(ascii)
    domain_ascii.value = ascii
    domain_display.value = display
}

<p>Try with your own data</p>

<label>
  <div>Input domain</div>
  <div><input id="domain" type="text"></div>
</label>
<div>Ascii: <output id="domain_ascii"></div>
<div>Display: <output id="domain_display"></div>