How to use Vercel Cloud Functions

January 23, 2021

Context

First Read My Article on Cloud Functions to understand why you should learn about them!

Getting Started

Create a new folder and initiate a git repo inside of it
in this folder create one new subfolder, api
Create an index.html in the main folder (just something for us to deploy)

<!DOCTYPE html>
<html lang="en">
  <head>
    <meta charset="UTF-8" />
    <meta name="viewport" content="width=device-width, initial-scale=1.0" />
    <title>Document</title>
  </head>
  <body>
    <h1>My Vercel Function Site!</h1>
  </body>
</html>

in the api folder create a first.js with the following

// Vercel Functions docs => https://vercel.com/docs/serverless-functions/introduction

module.exports = (req, res) => {
  res.json({
    body: req.body,
    query: req.query,
    cookies: req.cookies,
    hello: "world",
  })
}

now commit everything, push up to github and deploy to vercel
then to use this function the url would be…

https://myvercelurl/api/first

just to see it grab the url query try out

https://myvercelurl/api/first?cheese=gouda

Try using postman or CURL to make other types of requests like POST, PUT, DELETE

Other Things to Know

The req and res objects should work as they do in express.js
To enable cors just set the headers like so:

headers: {
      "Content-Type": "application/json",
      "Access-Control-Allow-Origin": "*",
      "Access-Control-Allow-Headers": "Content-Type",
      "Access-Control-Allow-Methods": "GET, POST, PUT, DELETE",
    }

If you are getting a cors error despite having the proper cors errors, it may be because the function is erroring