fetch-mocking

fetch-mock.js

const originalFetch = window.fetch

window.fetch = function (url, options = {}) {
  if (url === "http://example.net/locale") {
    return new Response(JSON.stringify({
              locale: "en-US",
              timeZone: "UTC"
    }))
  } else {
    throw Error(`${url} is not mocked.`)
  }
}

const resp = await fetch("http://example.net/locale")
const json = await resp.json()

console.log(json)
// {
//  "locale": "en-US",
//  "timeZone": "UTC"
// }

window.fetch = originalFetch