fetch-custom-error.js

const isOk = response => response.ok ? response.json() : Promise.reject(new Error('Failed to load data from server'))

fetch('https://api.github.com/orgs/nodejs')
.then(isOk) // <= Use `isOk` function here
.then(data => {
  console.log(data) // Prints result from `response.json()`
})
.catch(error => console.error(error))