added options and updated readme

.changeset/proud-beans-flow.md

@@ -0,0 +1,5 @@
+---
+"schemeit": minor
+---
+
+added options and updated readme

README.md

@@ -3,9 +3,48 @@
 # SchemeIt
 
 A lightweight express-js request validator, originally written for my personal projects and separated out into its own package for easier use.
+Schemeit will check individual elements against their chosen validators, ensure all non-optional elements are present in a payload and can also optionally enforce `noExtraElements` to prevent bloated payloads.
 
 ## Install
 
 ```
 npm install schemeit
 ```
+
+## Usage
+
+The following is a basic example usage of schemeit to build a validator middleware for an endpoint:
+
+```
+import express from "express";
+import { NumberValidator, StringValidator, validator } from '../Schemic';
+
+const app = express();
+
+const testValidator = validator({
+  name: StringValidator(),
+  age: NumberValidator.optional()
+});
+
+app.post('/test', testValidator, async (request: Request, response: Response) => {
+  response.status(200).json({ message: 'Success!' });
+});
+
+app.listen(3000);
+
+```
+
+You can also use the exported function `createValidator` to create your own validation function with custom rules like so:
+
+```
+const SpecificStringValidator: ValidationFunction = createValidator((object: unknown) => {
+  return object === 'foo' || object === 'bar';
+});
+```
+
+## Validator Options
+
+| Option          | Description                                                                                          |
+| --------------- | ---------------------------------------------------------------------------------------------------- |
+| noExtraElements | Rejects payloads with elements that do not exist in the validator schema                             |
+| errorListName   | Sets the name of the error list returned by the validator middleware, by default it is just `errors` |

src/@types/index.ts

@@ -3,6 +3,11 @@ export type DataTypeValidator = {
   optional?: boolean;
 };
 
+export type ValidatorOptions = {
+  noExtraElements?: boolean;
+  errorListName?: string;
+};
+
 export type ValidationFunction = (() => DataTypeValidator) & { optional: () => DataTypeValidator };
 export type ValidationError = Record<string, string>;
 export type Payload = Record<string, any> | null;

src/index.ts

@@ -1,5 +1,11 @@
 import { Request, Response, NextFunction, RequestHandler } from 'express';
-import { DataTypeValidator, ValidationError, Payload, ValidationFunction } from './@types/index';
+import {
+  DataTypeValidator,
+  ValidationError,
+  Payload,
+  ValidationFunction,
+  ValidatorOptions
+} from './@types/index';
 
 const extractPayload = (request: Request): Payload => {
   // eslint-disable-next-line @typescript-eslint/no-unsafe-argument
@@ -46,7 +52,10 @@ export const BooleanValidator = createValidator((object) => typeof object === 'b
  * @param validators The validation rules to follow
  * @returns {RequestHandler} An express middleware
  */
-export const validator = (validators: Record<string, DataTypeValidator>): RequestHandler => {
+export const validator = (
+  validators: Record<string, DataTypeValidator>,
+  options?: ValidatorOptions
+): RequestHandler => {
   return (request: Request, response: Response, next: NextFunction) => {
     const errors: ValidationError = {};
     const payload: Payload = extractPayload(request);
@@ -60,12 +69,21 @@ export const validator = (validators: Record<string, DataTypeValidator>): Reques
           errors[key] = 'Required element is missing or undefined';
         }
       } else if (!validator.validate(value)) {
-        errors[key] = 'Invalid type';
+        errors[key] = 'Invalid type: expected';
+      }
+    }
+
+    if (options?.noExtraElements) {
+      for (const key in payload) {
+        if (!validators[key]) {
+          errors[key] = 'Element does not exist in validator';
+        }
       }
     }
 
     if (Object.keys(errors).length) {
-      return response.status(400).json({ errors });
+      const errorResponseKey = options?.errorListName ? options.errorListName : 'errors';
+      return response.status(400).json({ [errorResponseKey]: errors });
     }
 
     next();