For anyone looking for a solution on a modern stack:
import jsonp from 'jsonp';
import queryString from 'query-string';
// formData being an object with your form data like:
// { EMAIL: '[email protected]' }
jsonp(`//YOURMAILCHIMP.us10.list-manage.com/subscribe/post-json?u=YOURMAILCHIMPU&${queryString.stringify(formData)}`, { param: 'c' }, (err, data) => {
console.log(err);
console.log(data);
});