Issue 4350 - Update punycode.js to 2.0.0

lib/punycode.js

Index: lib/punycode.js
diff --git a/lib/punycode.js b/lib/punycode.js
index 922669a30f65eff8028b7c675c80a21b6902bc5c..9d788aefb5908795e3a92f12da73091443676352 100644
--- a/lib/punycode.js
+++ b/lib/punycode.js
@@ -1,475 +1,440 @@
-/*! http://mths.be/punycode v1.2.3 by @mathias */
-/* Used under GPL 2.0, see https://github.com/bestiejs/punycode.js/blob/master/LICENSE-GPL.txt */
-;(function() {
-	/**
-	 * The `punycode` object.
-	 * @name punycode
-	 * @type Object
-	 */
-	var punycode,
-
-	/** Highest positive signed 32-bit float value */
-	maxInt = 2147483647, // aka. 0x7FFFFFFF or 2^31-1
-
-	/** Bootstring parameters */
-	base = 36,
-	tMin = 1,
-	tMax = 26,
-	skew = 38,
-	damp = 700,
-	initialBias = 72,
-	initialN = 128, // 0x80
-	delimiter = '-', // '\x2D'
-
-	/** Regular expressions */
-	regexPunycode = /^xn--/,
-	regexNonASCII = /[^ -~]/, // unprintable ASCII chars + non-ASCII chars
-	regexSeparators = /\x2E|\u3002|\uFF0E|\uFF61/g, // RFC 3490 separators
-
-	/** Error messages */
-	errors = {
-		'overflow': 'Overflow: input needs wider integers to process',
-		'not-basic': 'Illegal input >= 0x80 (not a basic code point)',
-		'invalid-input': 'Invalid input'
-	},
-
-	/** Convenience shortcuts */
-	baseMinusTMin = base - tMin,
-	floor = Math.floor,
-	stringFromCharCode = String.fromCharCode,
-
-	/** Temporary variable */
-	key;
-
-	/*--------------------------------------------------------------------------*/
-
-	/**
-	 * A generic error utility function.
-	 * @private
-	 * @param {String} type The error type.
-	 * @returns {Error} Throws a `RangeError` with the applicable error message.
-	 */
-	function error(type) {
-		throw RangeError(errors[type]);
+'use strict';
+
+/** Highest positive signed 32-bit float value */
+const maxInt = 2147483647; // aka. 0x7FFFFFFF or 2^31-1
+
+/** Bootstring parameters */
+const base = 36;
+const tMin = 1;
+const tMax = 26;
+const skew = 38;
+const damp = 700;
+const initialBias = 72;
+const initialN = 128; // 0x80
+const delimiter = '-'; // '\x2D'
+
+/** Regular expressions */
+const regexPunycode = /^xn--/;
+const regexNonASCII = /[^\x20-\x7E]/; // unprintable ASCII chars + non-ASCII chars
+const regexSeparators = /[\x2E\u3002\uFF0E\uFF61]/g; // RFC 3490 separators
+
+/** Error messages */
+const errors = {
+	'overflow': 'Overflow: input needs wider integers to process',
+	'not-basic': 'Illegal input >= 0x80 (not a basic code point)',
+	'invalid-input': 'Invalid input'
+};
+
+/** Convenience shortcuts */
+const baseMinusTMin = base - tMin;
+const floor = Math.floor;
+const stringFromCharCode = String.fromCharCode;
+
+/*--------------------------------------------------------------------------*/
+
+/**
+ * A generic error utility function.
+ * @private
+ * @param {String} type The error type.
+ * @returns {Error} Throws a `RangeError` with the applicable error message.
+ */
+function error(type) {
+	throw new RangeError(errors[type]);
+}
+
+/**
+ * A generic `Array#map` utility function.
+ * @private
+ * @param {Array} array The array to iterate over.
+ * @param {Function} callback The function that gets called for every array
+ * item.
+ * @returns {Array} A new array of values returned by the callback function.
+ */
+function map(array, fn) {
+	const result = [];
+	let length = array.length;
+	while (length--) {
+		result[length] = fn(array[length]);
 	}
-
-	/**
-	 * A generic `Array#map` utility function.
-	 * @private
-	 * @param {Array} array The array to iterate over.
-	 * @param {Function} callback The function that gets called for every array
-	 * item.
-	 * @returns {Array} A new array of values returned by the callback function.
-	 */
-	function map(array, fn) {
-		var length = array.length;
-		while (length--) {
-			array[length] = fn(array[length]);
-		}
-		return array;
-	}
-
-	/**
-	 * A simple `Array#map`-like wrapper to work with domain name strings.
-	 * @private
-	 * @param {String} domain The domain name.
-	 * @param {Function} callback The function that gets called for every
-	 * character.
-	 * @returns {Array} A new string of characters returned by the callback
-	 * function.
-	 */
-	function mapDomain(string, fn) {
-		return map(string.split(regexSeparators), fn).join('.');
+	return result;
+}
+
+/**
+ * A simple `Array#map`-like wrapper to work with domain name strings or email
+ * addresses.
+ * @private
+ * @param {String} domain The domain name or email address.
+ * @param {Function} callback The function that gets called for every
+ * character.
+ * @returns {Array} A new string of characters returned by the callback
+ * function.
+ */
+function mapDomain(string, fn) {
+	const parts = string.split('@');
+	let result = '';
+	if (parts.length > 1) {
+		// In email addresses, only the domain name should be punycoded. Leave
+		// the local part (i.e. everything up to `@`) intact.
+		result = parts[0] + '@';
+		string = parts[1];
 	}
-
-	/**
-	 * Creates an array containing the numeric code points of each Unicode
-	 * character in the string. While JavaScript uses UCS-2 internally,
-	 * this function will convert a pair of surrogate halves (each of which
-	 * UCS-2 exposes as separate characters) into a single code point,
-	 * matching UTF-16.
-	 * @see `punycode.ucs2.encode`
-	 * @see <http://mathiasbynens.be/notes/javascript-encoding>
-	 * @memberOf punycode.ucs2
-	 * @name decode
-	 * @param {String} string The Unicode input string (UCS-2).
-	 * @returns {Array} The new array of code points.
-	 */
-	function ucs2decode(string) {
-		var output = [],
-		    counter = 0,
-		    length = string.length,
-		    value,
-		    extra;
-		while (counter < length) {
-			value = string.charCodeAt(counter++);
-			if (value >= 0xD800 && value <= 0xDBFF && counter < length) {
-				// high surrogate, and there is a next character
-				extra = string.charCodeAt(counter++);
-				if ((extra & 0xFC00) == 0xDC00) { // low surrogate
-					output.push(((value & 0x3FF) << 10) + (extra & 0x3FF) + 0x10000);
-				} else {
-					// unmatched surrogate; only append this code unit, in case the next
-					// code unit is the high surrogate of a surrogate pair
-					output.push(value);
-					counter--;
-				}
+	// Avoid `split(regex)` for IE8 compatibility. See #17.
+	string = string.replace(regexSeparators, '\x2E');
+	const labels = string.split('.');
+	const encoded = map(labels, fn).join('.');
+	return result + encoded;
+}
+
+/**
+ * Creates an array containing the numeric code points of each Unicode
+ * character in the string. While JavaScript uses UCS-2 internally,
+ * this function will convert a pair of surrogate halves (each of which
+ * UCS-2 exposes as separate characters) into a single code point,
+ * matching UTF-16.
+ * @see `punycode.ucs2.encode`
+ * @see <https://mathiasbynens.be/notes/javascript-encoding>
+ * @memberOf punycode.ucs2
+ * @name decode
+ * @param {String} string The Unicode input string (UCS-2).
+ * @returns {Array} The new array of code points.
+ */
+function ucs2decode(string) {
+	const output = [];
+	let counter = 0;
+	const length = string.length;
+	while (counter < length) {
+		const value = string.charCodeAt(counter++);
+		if (value >= 0xD800 && value <= 0xDBFF && counter < length) {
+			// It's a high surrogate, and there is a next character.
+			const extra = string.charCodeAt(counter++);
+			if ((extra & 0xFC00) == 0xDC00) { // Low surrogate.
+				output.push(((value & 0x3FF) << 10) + (extra & 0x3FF) + 0x10000);
 			} else {
+				// It's an unmatched surrogate; only append this code unit, in case the
+				// next code unit is the high surrogate of a surrogate pair.
 				output.push(value);
+				counter--;
 			}
+		} else {
+			output.push(value);
 		}
-		return output;
 	}
-
-	/**
-	 * Creates a string based on an array of numeric code points.
-	 * @see `punycode.ucs2.decode`
-	 * @memberOf punycode.ucs2
-	 * @name encode
-	 * @param {Array} codePoints The array of numeric code points.
-	 * @returns {String} The new Unicode string (UCS-2).
-	 */
-	function ucs2encode(array) {
-		return map(array, function(value) {
-			var output = '';
-			if (value > 0xFFFF) {
-				value -= 0x10000;
-				output += stringFromCharCode(value >>> 10 & 0x3FF | 0xD800);
-				value = 0xDC00 | value & 0x3FF;
-			}
-			output += stringFromCharCode(value);
-			return output;
-		}).join('');
+	return output;
+}
+
+/**
+ * Creates a string based on an array of numeric code points.
+ * @see `punycode.ucs2.decode`
+ * @memberOf punycode.ucs2
+ * @name encode
+ * @param {Array} codePoints The array of numeric code points.
+ * @returns {String} The new Unicode string (UCS-2).
+ */
+const ucs2encode = array => String.fromCodePoint(...array);
+
+/**
+ * Converts a basic code point into a digit/integer.
+ * @see `digitToBasic()`
+ * @private
+ * @param {Number} codePoint The basic numeric code point value.
+ * @returns {Number} The numeric value of a basic code point (for use in
+ * representing integers) in the range `0` to `base - 1`, or `base` if
+ * the code point does not represent a value.
+ */
+const basicToDigit = function(codePoint) {
+	if (codePoint - 0x30 < 0x0A) {
+		return codePoint - 0x16;
 	}
-
-	/**
-	 * Converts a basic code point into a digit/integer.
-	 * @see `digitToBasic()`
-	 * @private
-	 * @param {Number} codePoint The basic numeric code point value.
-	 * @returns {Number} The numeric value of a basic code point (for use in
-	 * representing integers) in the range `0` to `base - 1`, or `base` if
-	 * the code point does not represent a value.
-	 */
-	function basicToDigit(codePoint) {
-		if (codePoint - 48 < 10) {
-			return codePoint - 22;
-		}
-		if (codePoint - 65 < 26) {
-			return codePoint - 65;
-		}
-		if (codePoint - 97 < 26) {
-			return codePoint - 97;
-		}
-		return base;
+	if (codePoint - 0x41 < 0x1A) {
+		return codePoint - 0x41;
 	}
-
-	/**
-	 * Converts a digit/integer into a basic code point.
-	 * @see `basicToDigit()`
-	 * @private
-	 * @param {Number} digit The numeric value of a basic code point.
-	 * @returns {Number} The basic code point whose value (when used for
-	 * representing integers) is `digit`, which needs to be in the range
-	 * `0` to `base - 1`. If `flag` is non-zero, the uppercase form is
-	 * used; else, the lowercase form is used. The behavior is undefined
-	 * if `flag` is non-zero and `digit` has no uppercase form.
-	 */
-	function digitToBasic(digit, flag) {
-		//  0..25 map to ASCII a..z or A..Z
-		// 26..35 map to ASCII 0..9
-		return digit + 22 + 75 * (digit < 26) - ((flag != 0) << 5);
+	if (codePoint - 0x61 < 0x1A) {
+		return codePoint - 0x61;
 	}
-
-	/**
-	 * Bias adaptation function as per section 3.4 of RFC 3492.
-	 * http://tools.ietf.org/html/rfc3492#section-3.4
-	 * @private
-	 */
-	function adapt(delta, numPoints, firstTime) {
-		var k = 0;
-		delta = firstTime ? floor(delta / damp) : delta >> 1;
-		delta += floor(delta / numPoints);
-		for (/* no initialization */; delta > baseMinusTMin * tMax >> 1; k += base) {
-			delta = floor(delta / baseMinusTMin);
-		}
-		return floor(k + (baseMinusTMin + 1) * delta / (delta + skew));
+	return base;
+};
+
+/**
+ * Converts a digit/integer into a basic code point.
+ * @see `basicToDigit()`
+ * @private
+ * @param {Number} digit The numeric value of a basic code point.
+ * @returns {Number} The basic code point whose value (when used for
+ * representing integers) is `digit`, which needs to be in the range
+ * `0` to `base - 1`. If `flag` is non-zero, the uppercase form is
+ * used; else, the lowercase form is used. The behavior is undefined
+ * if `flag` is non-zero and `digit` has no uppercase form.
+ */
+const digitToBasic = function(digit, flag) {
+	//  0..25 map to ASCII a..z or A..Z
+	// 26..35 map to ASCII 0..9
+	return digit + 22 + 75 * (digit < 26) - ((flag != 0) << 5);
+};
+
+/**
+ * Bias adaptation function as per section 3.4 of RFC 3492.
+ * https://tools.ietf.org/html/rfc3492#section-3.4
+ * @private
+ */
+const adapt = function(delta, numPoints, firstTime) {
+	let k = 0;
+	delta = firstTime ? floor(delta / damp) : delta >> 1;
+	delta += floor(delta / numPoints);
+	for (/* no initialization */; delta > baseMinusTMin * tMax >> 1; k += base) {
+		delta = floor(delta / baseMinusTMin);
+	}
+	return floor(k + (baseMinusTMin + 1) * delta / (delta + skew));
+};
+
+/**
+ * Converts a Punycode string of ASCII-only symbols to a string of Unicode
+ * symbols.
+ * @memberOf punycode
+ * @param {String} input The Punycode string of ASCII-only symbols.
+ * @returns {String} The resulting string of Unicode symbols.
+ */
+const decode = function(input) {
+	// Don't use UCS-2.
+	const output = [];
+	const inputLength = input.length;
+	let i = 0;
+	let n = initialN;
+	let bias = initialBias;
+
+	// 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.
+
+	let basic = input.lastIndexOf(delimiter);
+	if (basic < 0) {
+		basic = 0;
 	}
 
-	/**
-	 * Converts a Punycode string of ASCII-only symbols to a string of Unicode
-	 * symbols.
-	 * @memberOf punycode
-	 * @param {String} input The Punycode string of ASCII-only symbols.
-	 * @returns {String} The resulting string of Unicode symbols.
-	 */
-	function decode(input) {
-		// Don't use UCS-2
-		var output = [],
-		    inputLength = input.length,
-		    out,
-		    i = 0,
-		    n = initialN,
-		    bias = initialBias,
-		    basic,
-		    j,
-		    index,
-		    oldi,
-		    w,
-		    k,
-		    digit,
-		    t,
-		    length,
-		    /** Cached calculation results */
-		    baseMinusT;
-
-		// 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 (let j = 0; j < basic; ++j) {
+		// if it's not a basic code point
+		if (input.charCodeAt(j) >= 0x80) {
+			error('not-basic');
 		}
+		output.push(input.charCodeAt(j));
+	}
 
-		for (j = 0; j < basic; ++j) {
-			// if it's not a basic code point
-			if (input.charCodeAt(j) >= 0x80) {
-				error('not-basic');
-			}
-			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 (index = basic > 0 ? basic + 1 : 0; index < inputLength; /* no final expression */) {
-
-			// `index` 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; /* no condition */; k += base) {
+	// Main decoding loop: start just after the last delimiter if any basic code
+	// points were copied; start at the beginning otherwise.
 
-				if (index >= inputLength) {
-					error('invalid-input');
-				}
+	for (let index = basic > 0 ? basic + 1 : 0; index < inputLength; /* no final expression */) {
 
-				digit = basicToDigit(input.charCodeAt(index++));
+		// `index` 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`.
+		let oldi = i;
+		for (let w = 1, k = base; /* no condition */; k += base) {
 
-				if (digit >= base || digit > floor((maxInt - i) / w)) {
-					error('overflow');
-				}
-
-				i += digit * w;
-				t = k <= bias ? tMin : (k >= bias + tMax ? tMax : k - bias);
+			if (index >= inputLength) {
+				error('invalid-input');
+			}
 
-				if (digit < t) {
-					break;
-				}
+			const digit = basicToDigit(input.charCodeAt(index++));
 
-				baseMinusT = base - t;
-				if (w > floor(maxInt / baseMinusT)) {
-					error('overflow');
-				}
+			if (digit >= base || digit > floor((maxInt - i) / w)) {
+				error('overflow');
+			}
 
-				w *= baseMinusT;
+			i += digit * w;
+			const t = k <= bias ? tMin : (k >= bias + tMax ? tMax : k - bias);
 
+			if (digit < t) {
+				break;
 			}
 
-			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 (floor(i / out) > maxInt - n) {
+			const baseMinusT = base - t;
+			if (w > floor(maxInt / baseMinusT)) {
 				error('overflow');
 			}
 
-			n += floor(i / out);
-			i %= out;
-
-			// Insert `n` at position `i` of the output
-			output.splice(i++, 0, n);
+			w *= baseMinusT;
 
 		}
 
-		return ucs2encode(output);
-	}
+		const out = output.length + 1;
+		bias = adapt(i - oldi, out, oldi == 0);
 
-	/**
-	 * Converts a string of Unicode symbols to a Punycode string of ASCII-only
-	 * symbols.
-	 * @memberOf punycode
-	 * @param {String} input The string of Unicode symbols.
-	 * @returns {String} The resulting Punycode string of ASCII-only symbols.
-	 */
-	function encode(input) {
-		var n,
-		    delta,
-		    handledCPCount,
-		    basicLength,
-		    bias,
-		    j,
-		    m,
-		    q,
-		    k,
-		    t,
-		    currentValue,
-		    output = [],
-		    /** `inputLength` will hold the number of code points in `input`. */
-		    inputLength,
-		    /** Cached calculation results */
-		    handledCPCountPlusOne,
-		    baseMinusT,
-		    qMinusT;
-
-		// Convert the input in UCS-2 to Unicode
-		input = ucs2decode(input);
-
-		// Cache the length
-		inputLength = input.length;
-
-		// Initialize the state
-		n = initialN;
-		delta = 0;
-		bias = initialBias;
-
-		// Handle the basic code points
-		for (j = 0; j < inputLength; ++j) {
-			currentValue = input[j];
-			if (currentValue < 0x80) {
-				output.push(stringFromCharCode(currentValue));
-			}
+		// `i` was supposed to wrap around from `out` to `0`,
+		// incrementing `n` each time, so we'll fix that now:
+		if (floor(i / out) > maxInt - n) {
+			error('overflow');
 		}
 
-		handledCPCount = basicLength = output.length;
+		n += floor(i / out);
+		i %= out;
 
-		// `handledCPCount` is the number of code points that have been handled;
-		// `basicLength` is the number of basic code points.
+		// Insert `n` at position `i` of the output.
+		output.splice(i++, 0, n);
 
-		// Finish the basic string - if it is not empty - with a delimiter
-		if (basicLength) {
-			output.push(delimiter);
+	}
+
+	return String.fromCodePoint(...output);
+};
+
+/**
+ * Converts a string of Unicode symbols (e.g. a domain name label) to a
+ * Punycode string of ASCII-only symbols.
+ * @memberOf punycode
+ * @param {String} input The string of Unicode symbols.
+ * @returns {String} The resulting Punycode string of ASCII-only symbols.
+ */
+const encode = function(input) {
+	const output = [];
+
+	// Convert the input in UCS-2 to an array of Unicode code points.
+	input = ucs2decode(input);
+
+	// Cache the length.
+	let inputLength = input.length;
+
+	// Initialize the state.
+	let n = initialN;
+	let delta = 0;
+	let bias = initialBias;
+
+	// Handle the basic code points.
+	for (const currentValue of input) {
+		if (currentValue < 0x80) {
+			output.push(stringFromCharCode(currentValue));
 		}
+	}
 
-		// Main encoding loop:
-		while (handledCPCount < inputLength) {
+	let basicLength = output.length;
+	let handledCPCount = basicLength;
 
-			// All non-basic code points < n have been handled already. Find the next
-			// larger one:
-			for (m = maxInt, j = 0; j < inputLength; ++j) {
-				currentValue = input[j];
-				if (currentValue >= n && currentValue < m) {
-					m = currentValue;
-				}
-			}
+	// `handledCPCount` is the number of code points that have been handled;
+	// `basicLength` is the number of basic code points.
 
-			// Increase `delta` enough to advance the decoder's <n,i> state to <m,0>,
-			// but guard against overflow
-			handledCPCountPlusOne = handledCPCount + 1;
-			if (m - n > floor((maxInt - delta) / handledCPCountPlusOne)) {
-				error('overflow');
-			}
+	// Finish the basic string with a delimiter unless it's empty.
+	if (basicLength) {
+		output.push(delimiter);
+	}
 
-			delta += (m - n) * handledCPCountPlusOne;
-			n = m;
+	// Main encoding loop:
+	while (handledCPCount < inputLength) {
 
-			for (j = 0; j < inputLength; ++j) {
-				currentValue = input[j];
+		// All non-basic code points < n have been handled already. Find the next
+		// larger one:
+		let m = maxInt;
+		for (const currentValue of input) {
+			if (currentValue >= n && currentValue < m) {
+				m = currentValue;
+			}
+		}
 
-				if (currentValue < n && ++delta > maxInt) {
-					error('overflow');
-				}
+		// Increase `delta` enough to advance the decoder's <n,i> state to <m,0>,
+		// but guard against overflow.
+		const handledCPCountPlusOne = handledCPCount + 1;
+		if (m - n > floor((maxInt - delta) / handledCPCountPlusOne)) {
+			error('overflow');
+		}
 
-				if (currentValue == n) {
-					// Represent delta as a generalized variable-length integer
-					for (q = delta, k = base; /* no condition */; k += base) {
-						t = k <= bias ? tMin : (k >= bias + tMax ? tMax : k - bias);
-						if (q < t) {
-							break;
-						}
-						qMinusT = q - t;
-						baseMinusT = base - t;
-						output.push(
-							stringFromCharCode(digitToBasic(t + qMinusT % baseMinusT, 0))
-						);
-						q = floor(qMinusT / baseMinusT);
-					}
+		delta += (m - n) * handledCPCountPlusOne;
+		n = m;
 
-					output.push(stringFromCharCode(digitToBasic(q, 0)));
-					bias = adapt(delta, handledCPCountPlusOne, handledCPCount == basicLength);
-					delta = 0;
-					++handledCPCount;
+		for (const currentValue of input) {
+			if (currentValue < n && ++delta > maxInt) {
+				error('overflow');
+			}
+			if (currentValue == n) {
+				// Represent delta as a generalized variable-length integer.
+				let q = delta;
+				for (let k = base; /* no condition */; k += base) {
+					const t = k <= bias ? tMin : (k >= bias + tMax ? tMax : k - bias);
+					if (q < t) {
+						break;
+					}
+					const qMinusT = q - t;
+					const baseMinusT = base - t;
+					output.push(
+						stringFromCharCode(digitToBasic(t + qMinusT % baseMinusT, 0))
+					);
+					q = floor(qMinusT / baseMinusT);
 				}
+
+				output.push(stringFromCharCode(digitToBasic(q, 0)));
+				bias = adapt(delta, handledCPCountPlusOne, handledCPCount == basicLength);
+				delta = 0;
+				++handledCPCount;
 			}
+		}
 
-			++delta;
-			++n;
+		++delta;
+		++n;
 
-		}
-		return output.join('');
 	}
-
+	return output.join('');
+};
+
+/**
+ * Converts a Punycode string representing a domain name or an email address
+ * to Unicode. Only the Punycoded parts of the input will be converted, i.e.
+ * it doesn't matter if you call it on a string that has already been
+ * converted to Unicode.
+ * @memberOf punycode
+ * @param {String} input The Punycoded domain name or email address to
+ * convert to Unicode.
+ * @returns {String} The Unicode representation of the given Punycode
+ * string.
+ */
+const toUnicode = function(input) {
+	return mapDomain(input, function(string) {
+		return regexPunycode.test(string)
+			? decode(string.slice(4).toLowerCase())
+			: string;
+	});
+};
+
+/**
+ * Converts a Unicode string representing a domain name or an email address to
+ * Punycode. Only the non-ASCII parts of the domain name will be converted,
+ * i.e. it doesn't matter if you call it with a domain that's already in
+ * ASCII.
+ * @memberOf punycode
+ * @param {String} input The domain name or email address to convert, as a
+ * Unicode string.
+ * @returns {String} The Punycode representation of the given domain name or
+ * email address.
+ */
+const toASCII = function(input) {
+	return mapDomain(input, function(string) {
+		return regexNonASCII.test(string)
+			? 'xn--' + encode(string)
+			: string;
+	});
+};
+
+/*--------------------------------------------------------------------------*/
+
+/** Define the public API */
+const punycode = {
 	/**
-	 * Converts a Punycode string representing a domain name to Unicode. Only the
-	 * Punycoded parts of the domain name will be converted, i.e. it doesn't
-	 * matter if you call it on a string that has already been converted to
-	 * Unicode.
+	 * A string representing the current Punycode.js version number.
 	 * @memberOf punycode
-	 * @param {String} domain The Punycode domain name to convert to Unicode.
-	 * @returns {String} The Unicode representation of the given Punycode
-	 * string.
+	 * @type String
 	 */
-	function toUnicode(domain) {
-		return mapDomain(domain, function(string) {
-			return regexPunycode.test(string)
-				? decode(string.slice(4).toLowerCase())
-				: string;
-		});
-	}
-
+	'version': '2.0.0',
 	/**
-	 * Converts a Unicode string representing a domain name to Punycode. Only the
-	 * non-ASCII parts of the domain name will be converted, i.e. it doesn't
-	 * matter if you call it with a domain that's already in ASCII.
+	 * An object of methods to convert from JavaScript's internal character
+	 * representation (UCS-2) to Unicode code points, and back.
+	 * @see <https://mathiasbynens.be/notes/javascript-encoding>
 	 * @memberOf punycode
-	 * @param {String} domain The domain name to convert, as a Unicode string.
-	 * @returns {String} The Punycode representation of the given domain name.
+	 * @type Object
 	 */
-	function toASCII(domain) {
-		return mapDomain(domain, function(string) {
-			return regexNonASCII.test(string)
-				? 'xn--' + encode(string)
-				: string;
-		});
-	}
+	'ucs2': {
+		'decode': ucs2decode,
+		'encode': ucs2encode
+	},
+	'decode': decode,
+	'encode': encode,
+	'toASCII': toASCII,
+	'toUnicode': toUnicode
+};
 
-	/*--------------------------------------------------------------------------*/
-
-	/** Define the public API */
-	exports = {
-		/**
-		 * A string representing the current Punycode.js version number.
-		 * @memberOf punycode
-		 * @type String
-		 */
-		'version': '1.2.3',
-		/**
-		 * An object of methods to convert from JavaScript's internal character
-		 * representation (UCS-2) to Unicode code points, and back.
-		 * @see <http://mathiasbynens.be/notes/javascript-encoding>
-		 * @memberOf punycode
-		 * @type Object
-		 */
-		'ucs2': {
-			'decode': ucs2decode,
-			'encode': ucs2encode
-		},
-		'decode': decode,
-		'encode': encode,
-		'toASCII': toASCII,
-		'toUnicode': toUnicode
-	};
-}());
+module.exports = punycode;