Update README.md

README.md

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 # vercel-cors
+
+A simple CORS module for use with [Vercel Serverless Functions](https://vercel.com/docs/concepts/functions/serverless-functions). Also compatible with [Next.js API Routes](https://nextjs.org/docs/api-routes/introduction).
+
+## Installation
+```bash
+yarn add vercel-cors | npm i vercel-cors
+```
+
+## Usage
+Create your CORS configuration in a separated file:
+
+`config/cors.js`
+```javascript
+import cors from "vercel-cors"
+
+export default cors({
+  origin: '*' | string | RegExp | Array<string | RegExp>,
+  headers: string[],
+  methods: 'GET' | 'HEAD' | 'POST' | 'PUT' | 'PATCH' | 'UPDATE' | 'DELETE' | 'OPTIONS',
+  expose: string[],
+  maxAge: number | undefined,
+  credentials: boolean
+})
+```
+
+Then export as default a Higher Order Function passing your handler as parameter:
+
+`api/index.js`
+```javascript
+import withCors from "config/cors"
+
+async function handler (req, res) {
+  // do something
+}
+
+export default withCors(handler)
+```
+
+## Defaults options
+```javascript
+export const defaults = {
+  origin: '*',
+  headers: ['Origin', 'X-Requested-With', 'Content-Type', 'Accept'],
+  methods: ['GET', 'HEAD', 'POST', 'PUT', 'PATCH', 'UPDATE', 'OPTIONS', 'DELETE'],
+  expose: [],
+  maxAge: undefined,
+  credentials: false
+}
+```
+
+## Example
+```javascript
+import cors from "vercel-cors"
+
+export default cors({
+  origin: /^https:\/\/vercelproject-[a-z0-9]+-organization.vercel.app$/,
+  headers: ['Origin', 'X-Requested-With', 'Content-Type', 'Accept'],
+  methods: ['GET', 'POST', 'PUT', 'PATCH', 'UPDATE', 'DELETE'],
+  credentials: true
+})
+```
+
+## Multiple configurations
+Just export differents `cors()` functions from differents files:
+
+```
+config/cors
+├── dev.js
+└── prod.js
+```
+
+---
+**diegoulloao · 2022**