Revert "Revert "Cleanup some numeric code.""

fpdfsdk/src/javascript/util.cpp

Index: fpdfsdk/src/javascript/util.cpp
diff --git a/fpdfsdk/src/javascript/util.cpp b/fpdfsdk/src/javascript/util.cpp
index 14e15c1b6fac2b1ec932cbb7d5ad4462d225662b..cf10bbd7b42a376c30c50cc019bd34525e7f5a46 100644
--- a/fpdfsdk/src/javascript/util.cpp
+++ b/fpdfsdk/src/javascript/util.cpp
@@ -425,7 +425,7 @@ void util::printx(const std::string& cFormat,
         break;
       case 'X': {
         while (itSource < iSize) {
-          if ((cSource[itSource] >= '0' && cSource[itSource] <= '9') ||
+          if (std::isdigit(cSource[itSource]) ||
               (cSource[itSource] >= 'a' && cSource[itSource] <= 'z') ||
               (cSource[itSource] >= 'A' && cSource[itSource] <= 'Z')) {
             cPurpose += cSource[itSource];
@@ -450,7 +450,7 @@ void util::printx(const std::string& cFormat,
       } break;
       case '9': {
         while (itSource < iSize) {
-          if (cSource[itSource] >= '0' && cSource[itSource] <= '9') {
+          if (std::isdigit(cSource[itSource])) {
             cPurpose += cSource[itSource];
             itSource++;
             break;