Bump to v4.10.0.

truncate.js

@@ -1,5 +1,7 @@
+import castSlice from './_castSlice';
 import isObject from './isObject';
 import isRegExp from './isRegExp';
+import reHasComplexSymbol from './_reHasComplexSymbol';
 import stringSize from './_stringSize';
 import stringToArray from './_stringToArray';
 import toInteger from './toInteger';
@@ -12,18 +14,6 @@ var DEFAULT_TRUNC_LENGTH = 30,
 /** Used to match `RegExp` flags from their coerced string values. */
 var reFlags = /\w*$/;
 
-/** 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 + ']');
-
 /**
  * Truncates `string` if it's longer than the given maximum string length.
  * The last characters of the truncated string are replaced with the omission
@@ -85,7 +75,7 @@ function truncate(string, options) {
     return omission;
   }
   var result = strSymbols
-    ? strSymbols.slice(0, end).join('')
+    ? castSlice(strSymbols, 0, end).join('')
     : string.slice(0, end);
 
   if (separator === undefined) {