chore: error cleanup and docs

Author: georgejmx

README.md

@@ -366,6 +366,30 @@ jwt.verify(token, 'shhhhh', function(err, decoded) {
 });
 ```
 
+### InvalidPayloadError
+Thrown if the payload validation callback failed. The error message will be inherited from the error thrown in the `payloadCallback` or defaults to *'invalid token payload'* if for example a number was thrown and not an error
+
+Error object example:
+
+* name: 'InvalidPayloadError'
+* message: 'invalid token payload'
+
+```js
+jwt.verify(token, 'shhhhh', function(err, decoded) {
+  if (err) {
+    /*
+      err = {
+        name: 'InvalidPayloadError',
+        message: 'foo property not equal to bar',
+      }
+    */
+  }
+}, function (payload) {
+  if (payload.foo !== 'bar') {
+    throw new Error('foo property not equal to bar');
+  }
+});
+```
 
 ## Algorithms supported
 

lib/InvalidPayloadError.js

@@ -1,9 +1,8 @@
 const JsonWebTokenError = require("./JsonWebTokenError");
 
-const InvalidPayloadError = function (message, date) {
+const InvalidPayloadError = function (message) {
   JsonWebTokenError.call(this, message);
-  this.name = "InvalidFormatError";
-  this.date = date;
+  this.name = "InvalidPayloadError";
 };
 
 InvalidPayloadError.prototype = Object.create(JsonWebTokenError.prototype);