Added ability to keep previous exception handler

This adds a new boolean parameter, `keepPreviousHandler`. When set to true, it stores the previous handler value and calls it after calling the newly set exception handler. This allows developers to keep the previous functionality (red screen) intact, while still capturing errors (i.e. for analytics purposes).

Author: zeh

index.js

@@ -1,9 +1,17 @@
 const noop = () => {};
 
-export const setJSExceptionHandler = (customHandler = noop, allowedInDevMode = false) => {
+export const setJSExceptionHandler = (customHandler = noop, allowedInDevMode = false, keepPreviousHandler = false) => {
   const allowed = allowedInDevMode ? true : !__DEV__;
   if (allowed) {
-    global.ErrorUtils.setGlobalHandler(customHandler);
+    if (keepPreviousHandler) {
+      const previousHandler = global.ErrorUtils.getGlobalHandler();
+      global.ErrorUtils.setGlobalHandler((error, isFatal) => {
+        customHandler(error, isFatal);
+        previousHandler(error, isFatal);
+      });
+    } else {
+      global.ErrorUtils.setGlobalHandler(customHandler);
+    }
   } else {
     console.log('Skipping setJSExceptionHandler: Reason: In DEV mode and allowedInDevMode = false');
   }