I'm building a site with ES6 and Babel.

In a script file, I need to make an ajax call to a service on server. For that I'm doing like this:

fetch('url').then(

    response => response.json()

).then(

    supervisoryItems => doSomething(supervisoryItems)

)

In Google Chrome this works just fine, but it does not work on Firefox or IE (I'm getting the error fetch is undefined).
Searching on Google I found this should fix it:

import promise from 'es6-promise'

promise.polyfill()

Sadly it does not change anything, I have the same issue. Any help?