lib: remove unnecessary else statements (cloudevents#146)

This commit removes two unnecessary else clauses in unmarshaller.js, and
also extracts the throwing of TypeError of invalid content types into a
separate function to avoid some code duplication.

Signed-off-by: Daniel Bevenius <[email protected]>

Author: danbev

lib/bindings/http/unmarshaller.js

@@ -22,23 +22,23 @@ function resolveBindingName(payload, headers) {
     // Structured
     if (allowedStructuredContentTypes.includes(contentType)) {
       return STRUCTURED;
-    } else {
-      const err = new TypeError("structured+type not allowed");
-      err.errors = [contentType];
-      throw err;
     }
+    throwTypeError("structured+type not allowed", contentType);
   } else {
     // Binary
     if (allowedBinaryContentTypes.includes(contentType)) {
       return BINARY;
-    } else {
-      const err = new TypeError("content type not allowed");
-      err.errors = [contentType];
-      throw err;
     }
+    throwTypeError("content type not allowed", contentType);
   }
 }
 
+function throwTypeError(msg, contentType) {
+  const err = new TypeError(msg);
+  err.errors = [contentType];
+  throw err;
+}
+
 class Unmarshaller {
   constructor(receiverByBinding) {
     this.receiverByBinding = receiverByBinding;