How to Fix CORS Errors When Connecting an Angular Frontend to an Express Backend?

CORS Error: Resolving "Requests Are Only Supported for Protocol Schemes: http..."

When attempting to run an Express backend and retrieve a JSON string from a localhost link via Angular, a "CORS" error can occur. The error message typically indicates that cross-origin requests are only supported for specific protocol schemes.

To address this issue, several actions must be taken:

Firstly, ensure that the URL specified in the Angular Service includes the appropriate protocol scheme. In this instance, it should be "http". Change the base URL to:

this._baseUrl = 'http://localhost:4201/';

Secondly, verify that the Express server is correctly configured for CORS. Ensure that the cors module is being utilized properly, and consider explicitly setting the appropriate HTTP headers for CORS.

For example, in the handler function, you could add the following code to set the headers:

res.header('Access-Control-Allow-Origin', '*');
res.header("Access-Control-Allow-Headers", "Origin, X-Requested-With, Content-Type, Accept");

Additionally, consider examining the browser console and checking for any other error messages that could provide further insight into the problem.

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