Simplify charsLeftIndex and charsRightIndex.

lodash.js

@@ -384,11 +384,7 @@
     var index = -1,
         length = string.length;
 
-    while (++index < length) {
+    while (++index < length && chars.indexOf(string.charAt(index)) > -1) { }
-      if (chars.indexOf(string.charAt(index)) < 0) {
-        break;
-      }
-    }
     return index;
   }
 
@@ -404,11 +400,7 @@
   function charsRightIndex(string, chars) {
     var index = string.length;
 
-    while (index--) {
+    while (index-- && chars.indexOf(string.charAt(index)) > -1) { }
-      if (chars.indexOf(string.charAt(index)) < 0) {
-        break;
-      }
-    }
     return index;
   }