Bump to v4.10.0.

_createCaseFirst.js

@@ -1,20 +1,8 @@
-define(['./_stringToArray', './toString'], function(stringToArray, toString) {
+define(['./_castSlice', './_reHasComplexSymbol', './_stringToArray', './toString'], function(castSlice, reHasComplexSymbol, stringToArray, toString) {
 
   /** Used as a safe reference for `undefined` in pre-ES5 environments. */
   var undefined;
 
-  /** Used to compose unicode character classes. */
-  var rsAstralRange = '\\ud800-\\udfff',
-      rsComboMarksRange = '\\u0300-\\u036f\\ufe20-\\ufe23',
-      rsComboSymbolsRange = '\\u20d0-\\u20f0',
-      rsVarRange = '\\ufe0e\\ufe0f';
-
-  /** Used to compose unicode capture groups. */
-  var rsZWJ = '\\u200d';
-
-  /** Used to detect strings with [zero-width joiners or code points from the astral planes](http://eev.ee/blog/2015/09/12/dark-corners-of-unicode/). */
-  var reHasComplexSymbol = RegExp('[' + rsZWJ + rsAstralRange  + rsComboMarksRange + rsComboSymbolsRange + rsVarRange + ']');
-
   /**
    * Creates a function like `_.lowerFirst`.
    *
@@ -30,8 +18,13 @@ define(['./_stringToArray', './toString'], function(stringToArray, toString) {
         ? stringToArray(string)
         : undefined;
 
-      var chr = strSymbols ? strSymbols[0] : string.charAt(0),
-          trailing = strSymbols ? strSymbols.slice(1).join('') : string.slice(1);
+      var chr = strSymbols
+        ? strSymbols[0]
+        : string.charAt(0);
+
+      var trailing = strSymbols
+        ? castSlice(strSymbols, 1).join('')
+        : string.slice(1);
 
       return chr[methodName]() + trailing;
     };