Convert function expressions to arrow functions

As mentioned in slevithan/xregexp#108 (comment)

This was done with the help of [lebab], using `lebeb --replace src --transform arrow`.

[lebab]: https://github.com/lebab/lebab

I did have to add an `/* eslint disable no-confusing-arrow */` comment
to suppress an error. Once eslint/eslint#8439 is
merged and released, we can upgrade eslint and remove the comment.

src/addons/build.js

@@ -4,7 +4,7 @@
  * Steven Levithan (c) 2012-2017 MIT License
  */
 
-module.exports = function(XRegExp) {
+module.exports = (XRegExp) => {
     const REGEX_DATA = 'xregexp';
     const subParts = /(\()(?!\?)|\\([1-9]\d*)|\\[\s\S]|\[(?:[^\\\]]|\\[\s\S])*\]/g;
     const parts = XRegExp.union([/\({{([\w$]+)}}\)|{{([\w$]+)}}/, subParts], 'g', {
@@ -96,12 +96,10 @@ module.exports = function(XRegExp) {
      * time.test('10:59'); // -> true
      * XRegExp.exec('10:59', time).minutes; // -> '59'
      */
-    XRegExp.tag = function(flags) {
-        return function(literals, ...substitutions) {
-            const subpatterns = substitutions.map(interpolate).reduce(reduceToSubpatternsObject, {});
-            const pattern = literals.raw.map(embedSubpatternAfter).join('');
-            return XRegExp.build(pattern, subpatterns, flags);
-        };
+    XRegExp.tag = (flags) => (literals, ...substitutions) => {
+        const subpatterns = substitutions.map(interpolate).reduce(reduceToSubpatternsObject, {});
+        const pattern = literals.raw.map(embedSubpatternAfter).join('');
+        return XRegExp.build(pattern, subpatterns, flags);
     };
 
     /**
@@ -129,7 +127,7 @@ module.exports = function(XRegExp) {
      * time.test('10:59'); // -> true
      * XRegExp.exec('10:59', time).minutes; // -> '59'
      */
-    XRegExp.build = function(pattern, subs, flags) {
+    XRegExp.build = (pattern, subs, flags) => {
         flags = flags || '';
         // Used with `asXRegExp` calls for `pattern` and subpatterns in `subs`, to work around how
         // some browsers convert `RegExp('\n')` to a regex that contains the literal characters `\`
@@ -168,7 +166,7 @@ module.exports = function(XRegExp) {
         let numOuterCaps = 0;
         const outerCapsMap = [0];
         const outerCapNames = patternAsRegex[REGEX_DATA].captureNames || [];
-        const output = patternAsRegex.source.replace(parts, function($0, $1, $2, $3, $4) {
+        const output = patternAsRegex.source.replace(parts, ($0, $1, $2, $3, $4) => {
             const subName = $1 || $2;
             let capName;
             let intro;
@@ -189,7 +187,7 @@ module.exports = function(XRegExp) {
                     intro = '(?:';
                 }
                 numPriorCaps = numCaps;
-                return intro + data[subName].pattern.replace(subParts, function(match, paren, backref) {
+                return intro + data[subName].pattern.replace(subParts, (match, paren, backref) => {
                     // Capturing group
                     if (paren) {
                         capName = data[subName].names[numCaps - numPriorCaps];

src/addons/matchrecursive.js

@@ -4,7 +4,7 @@
  * Steven Levithan (c) 2009-2017 MIT License
  */
 
-module.exports = function(XRegExp) {
+module.exports = (XRegExp) => {
 
     /**
      * Returns a match detail object composed of the provided values.
@@ -70,7 +70,7 @@ module.exports = function(XRegExp) {
      * XRegExp.matchRecursive(str, '<', '>', 'gy');
      * // -> ['1', '<<2>>', '3']
      */
-    XRegExp.matchRecursive = function(str, left, right, flags, options) {
+    XRegExp.matchRecursive = (str, left, right, flags, options) => {
         flags = flags || '';
         options = options || {};
         const global = flags.indexOf('g') > -1;

src/addons/unicode-base.js

@@ -4,7 +4,7 @@
  * Steven Levithan (c) 2008-2017 MIT License
  */
 
-module.exports = function(XRegExp) {
+module.exports = (XRegExp) => {
 
     /**
      * Adds base support for Unicode matching:
@@ -53,7 +53,7 @@ module.exports = function(XRegExp) {
         XRegExp.forEach(
             range,
             /(\\x..|\\u....|\\?[\s\S])(?:-(\\x..|\\u....|\\?[\s\S]))?/,
-            function(m) {
+            (m) => {
                 const start = charCode(m[1]);
                 if (start > (lastEnd + 1)) {
                     output += '\\u' + pad4(hex(lastEnd + 1));
@@ -124,7 +124,7 @@ module.exports = function(XRegExp) {
     XRegExp.addToken(
         // Use `*` instead of `+` to avoid capturing `^` as the token name in `\p{^}`
         /\\([pP])(?:{(\^?)([^}]*)}|([A-Za-z]))/,
-        function(match, scope, flags) {
+        (match, scope, flags) => {
             const ERR_DOUBLE_NEG = 'Invalid double negation ';
             const ERR_UNKNOWN_NAME = 'Unknown Unicode token ';
             const ERR_UNKNOWN_REF = 'Unicode token missing data ';
@@ -206,7 +206,7 @@ module.exports = function(XRegExp) {
      * }]);
      * XRegExp('\\p{XDigit}:\\p{Hexadecimal}+').test('0:3D'); // -> true
      */
-    XRegExp.addUnicodeData = function(data) {
+    XRegExp.addUnicodeData = (data) => {
         const ERR_NO_NAME = 'Unicode token requires name';
         const ERR_NO_DATA = 'Unicode token has no character data ';
         let item;
@@ -251,7 +251,7 @@ module.exports = function(XRegExp) {
      * the future. It is meant for userland code that wishes to reuse the (large) internal Unicode
      * structures set up by XRegExp.
      */
-    XRegExp._getUnicodeProperty = function(name) {
+    XRegExp._getUnicodeProperty = (name) => {
         const slug = normalize(name);
         return unicode[slug];
     };

src/addons/unicode-blocks.js

@@ -5,7 +5,7 @@
  * Unicode data by Mathias Bynens <mathiasbynens.be>
  */
 
-module.exports = function(XRegExp) {
+module.exports = (XRegExp) => {
 
     /**
      * Adds support for all Unicode blocks. Block names use the prefix 'In'. E.g.,

src/addons/unicode-scripts.js

@@ -5,7 +5,7 @@
  * Unicode data by Mathias Bynens <mathiasbynens.be>
  */
 
-module.exports = function(XRegExp) {
+module.exports = (XRegExp) => {
 
     /**
      * Adds support for all Unicode scripts. E.g., `\p{Latin}`. Token names are case insensitive,