Merge pull request #1053 from BitGo/DX-1641-update-readme

docs: update README.md with information regarding new error formatters

Author: ericcrosson-bitgo

packages/typed-express-router/README.md

@@ -76,13 +76,19 @@ logging.
 
 ```ts
 const typedRouter = createRouter(MyApi, {
-  onDecodeError: (errs, req, res) => {
+  decodeErrorFormatter: (errs, req) => {
     // Format `errs` however you want
-    res.send(400).json({ message: 'Bad request' }).end();
+    return { message: 'Bad request' };
   },
-  onEncodeError: (err, req, res) => {
+  getDecodeErrorStatusCode: (errs, req) => {
+    return 400;
+  },
+  encodeErrorFormatter: (err, req) => {
+    return { message: 'Internal server error' };
+  },
+  getEncodeErrorStatusCode: (err, req) => {
     // Ideally won't happen unless type safety is violated, so it's a 500
-    res.send(500).json({ message: 'Internal server error' }).end();
+    return 500;
   },
   afterEncodedResponseSent: (status, payload, req, res) => {
     // Perform side effects or other things, `res` should be ended by this point
@@ -92,17 +98,18 @@ const typedRouter = createRouter(MyApi, {
 
 // Override the decode error handler on one route
 typedRouter.get('hello.world', [HelloWorldHandler], {
-  onDecodeError: customHelloDecodeErrorHandler,
+  decodeErrorFormatter: customHelloDecodeErrorFormatter,
 });
 ```
 
 ### Unchecked routes
 
 If you need custom behavior on decode errors that is more involved than just sending an
 error response, then the unchecked variant of the router functions can be used. They do
-not fail and call `onDecodeError` when a request is invalid. Instead, they will still
-populate `req.decoded`, except this time it'll contain the
-`Either<Errors, DecodedRequest>` type for route handlers to inspect.
+not fail and send a http response using `decodeErrorFormatter` and
+`getDecodeErrorStatusCode` when a request is invalid. Instead, they will still populate
+`req.decoded`, except this time it'll contain the `Either<Errors, DecodedRequest>` type
+for route handlers to inspect.
 
 ```ts
 // Just a normal express route