Problem with getting data with Fetch - JavaScript

Question

With the Postman program I download my shopping list from https://lit-brushlands-92375.herokuapp.com/api/items with GET

I would like to do the same in the browser console or on a website with code:

fetch('https://lit-brushlands-92375.herokuapp.com/api/items')
  .then(response => response.json())
  .then(data => console.log(data));

It returns the following error

VM89: 1 GET https://lit-brushlands-92375.herokuapp.com/api/items net :: ERR_FAILED

What am I doing wrong? What can be done better?

Answer 1

Front-end and Back-end are on Heroku. I received a CORS error. I added the following code to the main file of the back-end layer:

app.use((req, res, next) => {
    res.setHeader('Access-Control-Allow-Origin', '*');
    res.setHeader(
      'Access-Control-Allow-Headers',
      'Origin, X-Requested-With, Content-Type, Accept, Authorization'
    );
    res.setHeader('Access-Control-Allow-Methods', 'GET, POST, PATCH, DELETE');
  
    next();
  });

Thanks to this, I obtained a satisfactory effect in the form of downloaded data.