CORS and Prototyping with live APIs

Gary Meehan

by Gary Meehan

Frontend developer @ Distilled SCH

Over the last number of weeks I have been working with: Create React App, Razzle, After.js and Next.js to evaluate them for future projects. (More on this in a future post.) While doing this I wanted to use production APIs that I was familiar with so that I could focus only on the framework.

But there was one problem, APIs in all environments were missing one thing!

Access-Control-Allow-Origin: *

And with that you get:

No 'Access-Control-Allow-Origin' header is present on the requested resource. 
Origin 'http://localhost:3000' is therefore not allowed access. 
If an opaque response serves your needs, set the request's mode to 'no-cors' to fetch the resource with CORS disabled

Solution

Now there are many ways around this and I was looking for something super simple. I wanted something that I could share with the team and include as part of the prototype codebase. I found a couple of packages that offered parts of what I wanted. Some were full featured and ready for production! Others difficult to set up and unclear if they would work. In the end I created my own package (local-cors-proxy) that met my exact use case.

local-cors-proxy

The goal was simple, allow any API to be called without CORS issues and needing anything changed on the backend. This package does that by creating a simple proxy to bypass CORS issues. It is a dev only solution to help you rapidly prototype out your React / Vue / Angular (+ many many more) apps.

Getting started is easy, you can install the package globally or on a project by project basis.

Here is a simple example:

npm install -g local-cors-proxy

Take this as the example API endpoint that we are requesting that has CORS issues:

https://www.yourdomain.ie/movies/list

First we start the proxy:

lcp --proxyUrl https://www.yourdomain.ie

Then in your client code, the new API endpoint would look like:

http://localhost:8010/proxy/movies/list

End result will be a request to https://www.yourdomain.ie/movies/list without the CORS issues!

Alternatively you can install the package locally and add a script to your project:

"scripts": {    
  "proxy": "lcp --proxyUrl https://www.yourdomain.ie"  
}

And run it then via the command yarn proxy

Icon: block by Alina Oleynik from the Noun Project

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